diff --git a/toolchain/lowering/lowering_handle.cpp b/toolchain/lowering/lowering_handle.cpp
index 122ae8afd955..0a33da490327 100644
--- a/toolchain/lowering/lowering_handle.cpp
+++ b/toolchain/lowering/lowering_handle.cpp
@@ -24,6 +24,12 @@ auto LoweringHandleAddressOf(LoweringFunctionContext& context,
   context.SetLocal(node_id, context.GetLocal(node.GetAsAddressOf()));
 }
 
+auto LoweringHandleArrayIndex(LoweringFunctionContext& /*context*/,
+                              SemanticsNodeId /*node_id*/, SemanticsNode node)
+    -> void {
+  CARBON_FATAL() << "TODO: Add support: " << node;
+}
+
 auto LoweringHandleArrayType(LoweringFunctionContext& /*context*/,
                              SemanticsNodeId /*node_id*/, SemanticsNode node)
     -> void {
diff --git a/toolchain/semantics/semantics_handle_index.cpp b/toolchain/semantics/semantics_handle_index.cpp
index 8d8a682b61a8..d8a470ea6508 100644
--- a/toolchain/semantics/semantics_handle_index.cpp
+++ b/toolchain/semantics/semantics_handle_index.cpp
@@ -2,8 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-#include <cstdint>
-
+#include "toolchain/semantics/semantics_builtin_kind.h"
 #include "toolchain/semantics/semantics_context.h"
 #include "toolchain/semantics/semantics_node.h"
 #include "toolchain/semantics/semantics_node_kind.h"
@@ -19,6 +18,10 @@ auto SemanticsHandleIndexExpressionStart(SemanticsContext& /*context*/,
 
 auto SemanticsHandleIndexExpression(SemanticsContext& context,
                                     ParseTree::Node parse_node) -> bool {
+  CARBON_DIAGNOSTIC(OutOfBoundsAccess, Error,
+                    "Index `{0}` is past the end of `{1}`.", llvm::APSInt,
+                    std::string);
+
   auto index_node_id = context.node_stack().PopExpression();
   auto index_node = context.semantics_ir().GetNode(index_node_id);
   auto name_node_id = context.node_stack().PopExpression();
@@ -27,34 +30,57 @@ auto SemanticsHandleIndexExpression(SemanticsContext& context,
       context.semantics_ir().GetTypeAllowBuiltinTypes(name_node.type_id());
   auto name_type_node = context.semantics_ir().GetNode(name_type_id);
 
-  if (name_type_node.kind() == SemanticsNodeKind::TupleType &&
-      index_node.kind() == SemanticsNodeKind::IntegerLiteral) {
-    const auto& index_val = context.semantics_ir().GetIntegerLiteral(
-        index_node.GetAsIntegerLiteral());
-    auto type_block =
-        context.semantics_ir().GetTypeBlock(name_type_node.GetAsTupleType());
-
-    if (index_val.uge(static_cast<uint64_t>(type_block.size()))) {
-      CARBON_DIAGNOSTIC(OutOfBoundsAccess, Error,
-                        "Index `{0}` is past the end of `{1}`.", llvm::APSInt,
-                        std::string);
-      context.emitter().Emit(
-          parse_node, OutOfBoundsAccess,
-          llvm::APSInt(index_val, /*isUnsigned=*/true),
-          context.semantics_ir().StringifyType(name_node.type_id()));
-    } else {
+  if (name_type_node.kind() == SemanticsNodeKind::ArrayType) {
+    auto [bound_id, type_id] = name_type_node.GetAsArrayType();
+    if (index_node.kind() == SemanticsNodeKind::IntegerLiteral) {
+      const auto& index_val = context.semantics_ir().GetIntegerLiteral(
+          index_node.GetAsIntegerLiteral());
+      if (index_val.uge(context.semantics_ir().GetArrayBoundValue(bound_id))) {
+        context.emitter().Emit(
+            parse_node, OutOfBoundsAccess,
+            llvm::APSInt(index_val, /*isUnsigned=*/true),
+            context.semantics_ir().StringifyType(name_node.type_id()));
+      } else {
+        context.AddNodeAndPush(
+            parse_node, SemanticsNode::ArrayIndex::Make(
+                            parse_node, type_id, name_node_id, index_node_id));
+        return true;
+      }
+    } else if (context.ImplicitAsRequired(
+                   index_node.parse_node(), index_node_id,
+                   context.CanonicalizeType(
+                       SemanticsNodeId::BuiltinIntegerType)) !=
+               SemanticsNodeId::BuiltinError) {
       context.AddNodeAndPush(
-          parse_node, SemanticsNode::TupleIndex::Make(
-                          parse_node, type_block[index_val.getZExtValue()],
-                          name_node_id, index_node_id));
+          parse_node, SemanticsNode::ArrayIndex::Make(
+                          parse_node, type_id, name_node_id, index_node_id));
       return true;
     }
-  } else if (index_node.kind() != SemanticsNodeKind::IntegerLiteral) {
-    CARBON_DIAGNOSTIC(NondeterministicType, Error,
-                      "Type cannot be determined at compile time.");
-    context.emitter().Emit(parse_node, NondeterministicType);
-  } else if (name_type_node.kind() != SemanticsNodeKind::TupleType &&
-             name_type_id != SemanticsNodeId::BuiltinError) {
+  } else if (name_type_node.kind() == SemanticsNodeKind::TupleType) {
+    if (index_node.kind() == SemanticsNodeKind::IntegerLiteral) {
+      const auto& index_val = context.semantics_ir().GetIntegerLiteral(
+          index_node.GetAsIntegerLiteral());
+      auto type_block =
+          context.semantics_ir().GetTypeBlock(name_type_node.GetAsTupleType());
+
+      if (index_val.uge(static_cast<uint64_t>(type_block.size()))) {
+        context.emitter().Emit(
+            parse_node, OutOfBoundsAccess,
+            llvm::APSInt(index_val, /*isUnsigned=*/true),
+            context.semantics_ir().StringifyType(name_node.type_id()));
+      } else {
+        context.AddNodeAndPush(
+            parse_node, SemanticsNode::TupleIndex::Make(
+                            parse_node, type_block[index_val.getZExtValue()],
+                            name_node_id, index_node_id));
+        return true;
+      }
+    } else {
+      CARBON_DIAGNOSTIC(NondeterministicType, Error,
+                        "Type cannot be determined at compile time.");
+      context.emitter().Emit(parse_node, NondeterministicType);
+    }
+  } else if (name_type_id != SemanticsNodeId::BuiltinError) {
     CARBON_DIAGNOSTIC(InvalidIndexExpression, Error,
                       "Invalid index expression.");
     context.emitter().Emit(parse_node, InvalidIndexExpression);
diff --git a/toolchain/semantics/semantics_ir.cpp b/toolchain/semantics/semantics_ir.cpp
index 24502fbe90ea..d69b9f62259b 100644
--- a/toolchain/semantics/semantics_ir.cpp
+++ b/toolchain/semantics/semantics_ir.cpp
@@ -222,6 +222,7 @@ static auto GetTypePrecedence(SemanticsNodeKind kind) -> int {
       return 0;
 
     case SemanticsNodeKind::AddressOf:
+    case SemanticsNodeKind::ArrayIndex:
     case SemanticsNodeKind::ArrayValue:
     case SemanticsNodeKind::Assign:
     case SemanticsNodeKind::BinaryOperatorAdd:
@@ -376,6 +377,7 @@ auto SemanticsIR::StringifyType(SemanticsTypeId type_id,
         break;
       }
       case SemanticsNodeKind::AddressOf:
+      case SemanticsNodeKind::ArrayIndex:
       case SemanticsNodeKind::ArrayValue:
       case SemanticsNodeKind::Assign:
       case SemanticsNodeKind::BinaryOperatorAdd:
@@ -479,6 +481,12 @@ auto GetSemanticsExpressionCategory(const SemanticsIR& semantics_ir,
       case SemanticsNodeKind::UnaryOperatorNot:
         return SemanticsExpressionCategory::Value;
 
+      case SemanticsNodeKind::ArrayIndex: {
+        auto [base_id, index_id] = node.GetAsArrayIndex();
+        node_id = base_id;
+        continue;
+      }
+
       case SemanticsNodeKind::StructAccess: {
         auto [base_id, member_index] = node.GetAsStructAccess();
         node_id = base_id;
diff --git a/toolchain/semantics/semantics_node.h b/toolchain/semantics/semantics_node.h
index 1b93608c1d0b..f098659e7131 100644
--- a/toolchain/semantics/semantics_node.h
+++ b/toolchain/semantics/semantics_node.h
@@ -310,6 +310,10 @@ class SemanticsNode {
   using AddressOf = SemanticsNode::Factory<SemanticsNodeKind::AddressOf,
                                            SemanticsNodeId /*lvalue_id*/>;
 
+  using ArrayIndex =
+      Factory<SemanticsNodeKind::ArrayIndex, SemanticsNodeId /*array_id*/,
+              SemanticsNodeId /*index*/>;
+
   using ArrayType =
       SemanticsNode::Factory<SemanticsNodeKind::ArrayType,
                              SemanticsNodeId /*bound_node_id*/,
diff --git a/toolchain/semantics/semantics_node_kind.def b/toolchain/semantics/semantics_node_kind.def
index a04029853672..b95bb001f784 100644
--- a/toolchain/semantics/semantics_node_kind.def
+++ b/toolchain/semantics/semantics_node_kind.def
@@ -46,6 +46,7 @@ CARBON_SEMANTICS_NODE_KIND_IMPL(Invalid, "invalid", None, NotTerminator)
 CARBON_SEMANTICS_NODE_KIND_IMPL(CrossReference, "xref", Typed, NotTerminator)
 
 CARBON_SEMANTICS_NODE_KIND_IMPL(AddressOf, "address_of", Typed, NotTerminator)
+CARBON_SEMANTICS_NODE_KIND_IMPL(ArrayIndex, "array_index", Typed, NotTerminator)
 CARBON_SEMANTICS_NODE_KIND_IMPL(ArrayType, "array_type", Typed, NotTerminator)
 CARBON_SEMANTICS_NODE_KIND_IMPL(ArrayValue, "array_value", Typed, NotTerminator)
 CARBON_SEMANTICS_NODE_KIND_IMPL(Assign, "assign", None, NotTerminator)
diff --git a/toolchain/semantics/testdata/index/array_element_access.carbon b/toolchain/semantics/testdata/index/array_element_access.carbon
new file mode 100644
index 000000000000..8f87c6c1d79f
--- /dev/null
+++ b/toolchain/semantics/testdata/index/array_element_access.carbon
@@ -0,0 +1,126 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+
+var a: [i32; 2] = (12, 24);
+var b: i32 = 1;
+var c: i32 = a[0];
+var d: i32 = a[b];
+
+// CHECK:STDOUT: cross_reference_irs_size: 1
+// CHECK:STDOUT: functions: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: integer_literals: [
+// CHECK:STDOUT:   2,
+// CHECK:STDOUT:   12,
+// CHECK:STDOUT:   24,
+// CHECK:STDOUT:   1,
+// CHECK:STDOUT:   0,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: real_literals: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: strings: [
+// CHECK:STDOUT:   a,
+// CHECK:STDOUT:   b,
+// CHECK:STDOUT:   c,
+// CHECK:STDOUT:   d,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: types: [
+// CHECK:STDOUT:   nodeIntegerType,
+// CHECK:STDOUT:   node+1,
+// CHECK:STDOUT:   node+8,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: type_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     type0,
+// CHECK:STDOUT:     type0,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: nodes: [
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type0},
+// CHECK:STDOUT:   {kind: ArrayType, arg0: node+0, arg1: type0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: VarStorage, type: type1},
+// CHECK:STDOUT:   {kind: BindName, arg0: str0, arg1: node+2, type: type1},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
+// CHECK:STDOUT:   {kind: StubReference, arg0: node+4, type: type0},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int2, type: type0},
+// CHECK:STDOUT:   {kind: StubReference, arg0: node+6, type: type0},
+// CHECK:STDOUT:   {kind: TupleType, arg0: typeBlock0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: TupleValue, arg0: block2, type: type2},
+// CHECK:STDOUT:   {kind: ArrayValue, arg0: node+9, type: type1},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+2, arg1: node+10},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str1, arg1: node+12, type: type0},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int3, type: type0},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+12, arg1: node+14},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str2, arg1: node+16, type: type0},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int4, type: type0},
+// CHECK:STDOUT:   {kind: ArrayIndex, arg0: node+2, arg1: node+18, type: type0},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+16, arg1: node+19},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str3, arg1: node+21, type: type0},
+// CHECK:STDOUT:   {kind: ArrayIndex, arg0: node+2, arg1: node+12, type: type0},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+21, arg1: node+23},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: node_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+0,
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+2,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+4,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:     node+6,
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:     node+8,
+// CHECK:STDOUT:     node+9,
+// CHECK:STDOUT:     node+10,
+// CHECK:STDOUT:     node+11,
+// CHECK:STDOUT:     node+12,
+// CHECK:STDOUT:     node+13,
+// CHECK:STDOUT:     node+14,
+// CHECK:STDOUT:     node+15,
+// CHECK:STDOUT:     node+16,
+// CHECK:STDOUT:     node+17,
+// CHECK:STDOUT:     node+18,
+// CHECK:STDOUT:     node+19,
+// CHECK:STDOUT:     node+20,
+// CHECK:STDOUT:     node+21,
+// CHECK:STDOUT:     node+22,
+// CHECK:STDOUT:     node+23,
+// CHECK:STDOUT:     node+24,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT:
+// CHECK:STDOUT: package {
+// CHECK:STDOUT:   %.loc7_14: i32 = int_literal 2
+// CHECK:STDOUT:   %.loc7_15: type = array_type %.loc7_14, i32
+// CHECK:STDOUT:   %a: [i32; 2] = var
+// CHECK:STDOUT:   %.loc7_20.1: i32 = int_literal 12
+// CHECK:STDOUT:   %.loc7_20.2: i32 = stub_reference %.loc7_20.1
+// CHECK:STDOUT:   %.loc7_24.1: i32 = int_literal 24
+// CHECK:STDOUT:   %.loc7_24.2: i32 = stub_reference %.loc7_24.1
+// CHECK:STDOUT:   %.loc7_26.1: type = tuple_type (i32, i32)
+// CHECK:STDOUT:   %.loc7_26.2: (i32, i32) = tuple_value (%.loc7_20.2, %.loc7_24.2)
+// CHECK:STDOUT:   %.loc7_26.3: [i32; 2] = array_value %.loc7_26.2
+// CHECK:STDOUT:   assign %a, %.loc7_26.3
+// CHECK:STDOUT:   %b: i32 = var
+// CHECK:STDOUT:   %.loc8: i32 = int_literal 1
+// CHECK:STDOUT:   assign %b, %.loc8
+// CHECK:STDOUT:   %c: i32 = var
+// CHECK:STDOUT:   %.loc9_16: i32 = int_literal 0
+// CHECK:STDOUT:   %.loc9_17: i32 = array_index %a, %.loc9_16
+// CHECK:STDOUT:   assign %c, %.loc9_17
+// CHECK:STDOUT:   %d: i32 = var
+// CHECK:STDOUT:   %.loc10: i32 = array_index %a, %b
+// CHECK:STDOUT:   assign %d, %.loc10
+// CHECK:STDOUT: }
diff --git a/toolchain/semantics/testdata/index/fail_array_large_index.carbon b/toolchain/semantics/testdata/index/fail_array_large_index.carbon
new file mode 100644
index 000000000000..7ae6fc4a62ad
--- /dev/null
+++ b/toolchain/semantics/testdata/index/fail_array_large_index.carbon
@@ -0,0 +1,90 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+
+var a: [i32; 1] = (12,);
+// CHECK:STDERR: fail_array_large_index.carbon:[[@LINE+3]]:35: Index `295147905179352825855` is past the end of `[i32; 1]`.
+// CHECK:STDERR: var b: i32 = a[0xFFFFFFFFFFFFFFFFF];
+// CHECK:STDERR:                                   ^
+var b: i32 = a[0xFFFFFFFFFFFFFFFFF];
+
+// CHECK:STDOUT: cross_reference_irs_size: 1
+// CHECK:STDOUT: functions: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: integer_literals: [
+// CHECK:STDOUT:   1,
+// CHECK:STDOUT:   12,
+// CHECK:STDOUT:   -1,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: real_literals: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: strings: [
+// CHECK:STDOUT:   a,
+// CHECK:STDOUT:   b,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: types: [
+// CHECK:STDOUT:   nodeIntegerType,
+// CHECK:STDOUT:   node+1,
+// CHECK:STDOUT:   node+6,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: type_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     type0,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: nodes: [
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type0},
+// CHECK:STDOUT:   {kind: ArrayType, arg0: node+0, arg1: type0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: VarStorage, type: type1},
+// CHECK:STDOUT:   {kind: BindName, arg0: str0, arg1: node+2, type: type1},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
+// CHECK:STDOUT:   {kind: StubReference, arg0: node+4, type: type0},
+// CHECK:STDOUT:   {kind: TupleType, arg0: typeBlock0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: TupleValue, arg0: block2, type: type2},
+// CHECK:STDOUT:   {kind: ArrayValue, arg0: node+7, type: type1},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+2, arg1: node+8},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str1, arg1: node+10, type: type0},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int2, type: type0},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+10, arg1: nodeError},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: node_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+0,
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+2,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+4,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:     node+6,
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:     node+8,
+// CHECK:STDOUT:     node+9,
+// CHECK:STDOUT:     node+10,
+// CHECK:STDOUT:     node+11,
+// CHECK:STDOUT:     node+12,
+// CHECK:STDOUT:     node+13,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT:
+// CHECK:STDOUT: package {
+// CHECK:STDOUT:   %.loc7_14: i32 = int_literal 1
+// CHECK:STDOUT:   %.loc7_15: type = array_type %.loc7_14, i32
+// CHECK:STDOUT:   %a: [i32; 1] = var
+// CHECK:STDOUT:   %.loc7_20.1: i32 = int_literal 12
+// CHECK:STDOUT:   %.loc7_20.2: i32 = stub_reference %.loc7_20.1
+// CHECK:STDOUT:   %.loc7_23.1: type = tuple_type (i32)
+// CHECK:STDOUT:   %.loc7_23.2: (i32,) = tuple_value (%.loc7_20.2)
+// CHECK:STDOUT:   %.loc7_23.3: [i32; 1] = array_value %.loc7_23.2
+// CHECK:STDOUT:   assign %a, %.loc7_23.3
+// CHECK:STDOUT:   %b: i32 = var
+// CHECK:STDOUT:   %.loc11: i32 = int_literal -1
+// CHECK:STDOUT:   assign %b, <error>
+// CHECK:STDOUT: }
diff --git a/toolchain/semantics/testdata/index/fail_array_non_int_indexing.carbon b/toolchain/semantics/testdata/index/fail_array_non_int_indexing.carbon
new file mode 100644
index 000000000000..634ac04a5783
--- /dev/null
+++ b/toolchain/semantics/testdata/index/fail_array_non_int_indexing.carbon
@@ -0,0 +1,91 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+
+var a: [i32; 1] = (12,);
+// CHECK:STDERR: fail_array_non_int_indexing.carbon:[[@LINE+3]]:16: Cannot implicitly convert from `f64` to `i32`.
+// CHECK:STDERR: var b: i32 = a[2.6];
+// CHECK:STDERR:                ^
+var b: i32 = a[2.6];
+
+// CHECK:STDOUT: cross_reference_irs_size: 1
+// CHECK:STDOUT: functions: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: integer_literals: [
+// CHECK:STDOUT:   1,
+// CHECK:STDOUT:   12,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: real_literals: [
+// CHECK:STDOUT:   {mantissa: 26, exponent: -1, is_decimal: 1},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: strings: [
+// CHECK:STDOUT:   a,
+// CHECK:STDOUT:   b,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: types: [
+// CHECK:STDOUT:   nodeIntegerType,
+// CHECK:STDOUT:   node+1,
+// CHECK:STDOUT:   node+6,
+// CHECK:STDOUT:   nodeFloatingPointType,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: type_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     type0,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: nodes: [
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type0},
+// CHECK:STDOUT:   {kind: ArrayType, arg0: node+0, arg1: type0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: VarStorage, type: type1},
+// CHECK:STDOUT:   {kind: BindName, arg0: str0, arg1: node+2, type: type1},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
+// CHECK:STDOUT:   {kind: StubReference, arg0: node+4, type: type0},
+// CHECK:STDOUT:   {kind: TupleType, arg0: typeBlock0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: TupleValue, arg0: block2, type: type2},
+// CHECK:STDOUT:   {kind: ArrayValue, arg0: node+7, type: type1},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+2, arg1: node+8},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str1, arg1: node+10, type: type0},
+// CHECK:STDOUT:   {kind: RealLiteral, arg0: real0, type: type3},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+10, arg1: nodeError},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: node_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+0,
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+2,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+4,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:     node+6,
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:     node+8,
+// CHECK:STDOUT:     node+9,
+// CHECK:STDOUT:     node+10,
+// CHECK:STDOUT:     node+11,
+// CHECK:STDOUT:     node+12,
+// CHECK:STDOUT:     node+13,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT:
+// CHECK:STDOUT: package {
+// CHECK:STDOUT:   %.loc7_14: i32 = int_literal 1
+// CHECK:STDOUT:   %.loc7_15: type = array_type %.loc7_14, i32
+// CHECK:STDOUT:   %a: [i32; 1] = var
+// CHECK:STDOUT:   %.loc7_20.1: i32 = int_literal 12
+// CHECK:STDOUT:   %.loc7_20.2: i32 = stub_reference %.loc7_20.1
+// CHECK:STDOUT:   %.loc7_23.1: type = tuple_type (i32)
+// CHECK:STDOUT:   %.loc7_23.2: (i32,) = tuple_value (%.loc7_20.2)
+// CHECK:STDOUT:   %.loc7_23.3: [i32; 1] = array_value %.loc7_23.2
+// CHECK:STDOUT:   assign %a, %.loc7_23.3
+// CHECK:STDOUT:   %b: i32 = var
+// CHECK:STDOUT:   %.loc11: f64 = real_literal 26e-1
+// CHECK:STDOUT:   assign %b, <error>
+// CHECK:STDOUT: }
diff --git a/toolchain/semantics/testdata/index/fail_array_out_of_bound_access.carbon b/toolchain/semantics/testdata/index/fail_array_out_of_bound_access.carbon
new file mode 100644
index 000000000000..6594e9db2e39
--- /dev/null
+++ b/toolchain/semantics/testdata/index/fail_array_out_of_bound_access.carbon
@@ -0,0 +1,90 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+
+var a: [i32; 1] = (12,);
+// CHECK:STDERR: fail_array_out_of_bound_access.carbon:[[@LINE+3]]:17: Index `2` is past the end of `[i32; 1]`.
+// CHECK:STDERR: var b: i32 = a[2];
+// CHECK:STDERR:                 ^
+var b: i32 = a[2];
+
+// CHECK:STDOUT: cross_reference_irs_size: 1
+// CHECK:STDOUT: functions: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: integer_literals: [
+// CHECK:STDOUT:   1,
+// CHECK:STDOUT:   12,
+// CHECK:STDOUT:   2,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: real_literals: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: strings: [
+// CHECK:STDOUT:   a,
+// CHECK:STDOUT:   b,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: types: [
+// CHECK:STDOUT:   nodeIntegerType,
+// CHECK:STDOUT:   node+1,
+// CHECK:STDOUT:   node+6,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: type_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     type0,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: nodes: [
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type0},
+// CHECK:STDOUT:   {kind: ArrayType, arg0: node+0, arg1: type0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: VarStorage, type: type1},
+// CHECK:STDOUT:   {kind: BindName, arg0: str0, arg1: node+2, type: type1},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
+// CHECK:STDOUT:   {kind: StubReference, arg0: node+4, type: type0},
+// CHECK:STDOUT:   {kind: TupleType, arg0: typeBlock0, type: typeTypeType},
+// CHECK:STDOUT:   {kind: TupleValue, arg0: block2, type: type2},
+// CHECK:STDOUT:   {kind: ArrayValue, arg0: node+7, type: type1},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+2, arg1: node+8},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str1, arg1: node+10, type: type0},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int2, type: type0},
+// CHECK:STDOUT:   {kind: Assign, arg0: node+10, arg1: nodeError},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: node_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+0,
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+2,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+4,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:     node+6,
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:     node+8,
+// CHECK:STDOUT:     node+9,
+// CHECK:STDOUT:     node+10,
+// CHECK:STDOUT:     node+11,
+// CHECK:STDOUT:     node+12,
+// CHECK:STDOUT:     node+13,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+// CHECK:STDOUT:
+// CHECK:STDOUT: package {
+// CHECK:STDOUT:   %.loc7_14: i32 = int_literal 1
+// CHECK:STDOUT:   %.loc7_15: type = array_type %.loc7_14, i32
+// CHECK:STDOUT:   %a: [i32; 1] = var
+// CHECK:STDOUT:   %.loc7_20.1: i32 = int_literal 12
+// CHECK:STDOUT:   %.loc7_20.2: i32 = stub_reference %.loc7_20.1
+// CHECK:STDOUT:   %.loc7_23.1: type = tuple_type (i32)
+// CHECK:STDOUT:   %.loc7_23.2: (i32,) = tuple_value (%.loc7_20.2)
+// CHECK:STDOUT:   %.loc7_23.3: [i32; 1] = array_value %.loc7_23.2
+// CHECK:STDOUT:   assign %a, %.loc7_23.3
+// CHECK:STDOUT:   %b: i32 = var
+// CHECK:STDOUT:   %.loc11: i32 = int_literal 2
+// CHECK:STDOUT:   assign %b, <error>
+// CHECK:STDOUT: }
diff --git a/toolchain/semantics/testdata/index/fail_large_index.carbon b/toolchain/semantics/testdata/index/fail_tuple_large_index.carbon
similarity index 97%
rename from toolchain/semantics/testdata/index/fail_large_index.carbon
rename to toolchain/semantics/testdata/index/fail_tuple_large_index.carbon
index 786ce8e90e84..0e22252892ae 100644
--- a/toolchain/semantics/testdata/index/fail_large_index.carbon
+++ b/toolchain/semantics/testdata/index/fail_tuple_large_index.carbon
@@ -6,7 +6,7 @@
 
 var a: (i32,) = (12,);
 var b: (i32,) = a;
-// CHECK:STDERR: fail_large_index.carbon:[[@LINE+3]]:35: Index `295147905179352825855` is past the end of `(i32,) as type`.
+// CHECK:STDERR: fail_tuple_large_index.carbon:[[@LINE+3]]:35: Index `295147905179352825855` is past the end of `(i32,) as type`.
 // CHECK:STDERR: var c: i32 = b[0xFFFFFFFFFFFFFFFFF];
 // CHECK:STDERR:                                   ^
 var c: i32 = b[0xFFFFFFFFFFFFFFFFF];
diff --git a/toolchain/semantics/testdata/index/fail_non_int_indexing.carbon b/toolchain/semantics/testdata/index/fail_tuple_non_int_indexing.carbon
similarity index 97%
rename from toolchain/semantics/testdata/index/fail_non_int_indexing.carbon
rename to toolchain/semantics/testdata/index/fail_tuple_non_int_indexing.carbon
index e3d2fc94f554..f1b89b65d0df 100644
--- a/toolchain/semantics/testdata/index/fail_non_int_indexing.carbon
+++ b/toolchain/semantics/testdata/index/fail_tuple_non_int_indexing.carbon
@@ -5,7 +5,7 @@
 // AUTOUPDATE
 
 var a: (i32, i32) = (12, 6);
-// CHECK:STDERR: fail_non_int_indexing.carbon:[[@LINE+3]]:19: Type cannot be determined at compile time.
+// CHECK:STDERR: fail_tuple_non_int_indexing.carbon:[[@LINE+3]]:19: Type cannot be determined at compile time.
 // CHECK:STDERR: var b: i32 = a[2.6];
 // CHECK:STDERR:                   ^
 var b: i32 = a[2.6];
diff --git a/toolchain/semantics/testdata/index/fail_out_of_bound_access.carbon b/toolchain/semantics/testdata/index/fail_tuple_out_of_bound_access.carbon
similarity index 97%
rename from toolchain/semantics/testdata/index/fail_out_of_bound_access.carbon
rename to toolchain/semantics/testdata/index/fail_tuple_out_of_bound_access.carbon
index ef0e1eb62af7..2d7a0ebb4817 100644
--- a/toolchain/semantics/testdata/index/fail_out_of_bound_access.carbon
+++ b/toolchain/semantics/testdata/index/fail_tuple_out_of_bound_access.carbon
@@ -5,7 +5,7 @@
 // AUTOUPDATE
 
 var a: (i32, i32) = (12, 6);
-// CHECK:STDERR: fail_out_of_bound_access.carbon:[[@LINE+3]]:17: Index `2` is past the end of `(i32, i32) as type`.
+// CHECK:STDERR: fail_tuple_out_of_bound_access.carbon:[[@LINE+3]]:17: Index `2` is past the end of `(i32, i32) as type`.
 // CHECK:STDERR: var b: i32 = a[2];
 // CHECK:STDERR:                 ^
 var b: i32 = a[2];
diff --git a/toolchain/semantics/testdata/index/element_access.carbon b/toolchain/semantics/testdata/index/tuple_element_access.carbon
similarity index 100%
rename from toolchain/semantics/testdata/index/element_access.carbon
rename to toolchain/semantics/testdata/index/tuple_element_access.carbon
diff --git a/toolchain/semantics/testdata/index/return_value_access.carbon b/toolchain/semantics/testdata/index/tuple_return_value_access.carbon
similarity index 100%
rename from toolchain/semantics/testdata/index/return_value_access.carbon
rename to toolchain/semantics/testdata/index/tuple_return_value_access.carbon