diff --git a/executable_semantics/BUILD b/executable_semantics/BUILD
index b8e48a0a7135..a5f4ff86d565 100644
--- a/executable_semantics/BUILD
+++ b/executable_semantics/BUILD
@@ -12,7 +12,7 @@ cc_binary(
     name = "executable_semantics",
     srcs = ["main.cpp"],
     deps = [
-        ":syntax",
+        "//executable_semantics/syntax",
         "@llvm-project//llvm:Support",
     ],
 )
@@ -21,61 +21,7 @@ cc_library(
     name = "tracing_flag",
     srcs = ["tracing_flag.cpp"],
     hdrs = ["tracing_flag.h"],
-    visibility = ["//visibility:public"],
-)
-
-cc_library(
-    name = "syntax",
-    srcs = [
-        "syntax.tab.cpp",
-        "syntax.yy.cpp",
-        "syntax_helpers.cpp",
-        "syntax_helpers.h",
-    ],
-    hdrs = ["syntax.tab.h"],
-    # Disable warnings for generated code.
-    copts = [
-        "-Wno-unneeded-internal-declaration",
-        "-Wno-unused-function",
-        "-Wno-writable-strings",
-    ],
-    deps = [
-        ":tracing_flag",
-        "//executable_semantics/ast:declaration",
-        "//executable_semantics/ast:expression",
-        "//executable_semantics/ast:field_list",
-        "//executable_semantics/interpreter",
-    ],
-)
-
-genrule(
-    name = "syntax_bison_srcs",
-    srcs = ["syntax.ypp"],
-    outs = [
-        "syntax.tab.cpp",
-        "syntax.tab.h",
-    ],
-    cmd = "M4=$(M4) $(BISON) " +
-          "--output=$(location syntax.tab.cpp) " +
-          "--defines=$(location syntax.tab.h) " +
-          "$(location syntax.ypp)",
-    toolchains = [
-        "@rules_bison//bison:current_bison_toolchain",
-        "@rules_m4//m4:current_m4_toolchain",
-    ],
-)
-
-genrule(
-    name = "syntax_flex_srcs",
-    srcs = ["syntax.lpp"],
-    outs = ["syntax.yy.cpp"],
-    cmd = "M4=$(M4) $(FLEX) " +
-          "--outfile=$(location syntax.yy.cpp) " +
-          "$(location syntax.lpp)",
-    toolchains = [
-        "@rules_flex//flex:current_flex_toolchain",
-        "@rules_m4//m4:current_m4_toolchain",
-    ],
+    visibility = ["//executable_semantics:__subpackages__"],
 )
 
 EXAMPLES = [
diff --git a/executable_semantics/main.cpp b/executable_semantics/main.cpp
index fe2d099f03c6..84ad6a9c40bd 100644
--- a/executable_semantics/main.cpp
+++ b/executable_semantics/main.cpp
@@ -6,7 +6,7 @@
 #include <cstring>
 #include <iostream>
 
-#include "executable_semantics/syntax_helpers.h"
+#include "executable_semantics/syntax/syntax_helpers.h"
 #include "executable_semantics/tracing_flag.h"
 #include "llvm/Support/CommandLine.h"
 
diff --git a/executable_semantics/syntax/BUILD b/executable_semantics/syntax/BUILD
new file mode 100644
index 000000000000..0d13a31ee9bb
--- /dev/null
+++ b/executable_semantics/syntax/BUILD
@@ -0,0 +1,64 @@
+# 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
+
+# TODO(https://github.com/carbon-language/carbon-lang/issues/266):
+# Migrate bison/flex usage to a more hermetic bazel build.
+
+load("@rules_cc//cc:defs.bzl", "cc_binary", "cc_library")
+
+package(default_visibility = ["//executable_semantics:__subpackages__"])
+
+cc_library(
+    name = "syntax",
+    srcs = [
+        "syntax.tab.cpp",
+        "syntax.yy.cpp",
+        "syntax_helpers.cpp",
+        "syntax_helpers.h",
+    ],
+    hdrs = ["syntax.tab.h"],
+    # Disable warnings for generated code.
+    copts = [
+        "-Wno-unneeded-internal-declaration",
+        "-Wno-unused-function",
+        "-Wno-writable-strings",
+    ],
+    deps = [
+        "//executable_semantics:tracing_flag",
+        "//executable_semantics/ast:declaration",
+        "//executable_semantics/ast:expression",
+        "//executable_semantics/ast:field_list",
+        "//executable_semantics/interpreter",
+    ],
+)
+
+genrule(
+    name = "syntax_bison_srcs",
+    srcs = ["syntax.ypp"],
+    outs = [
+        "syntax.tab.cpp",
+        "syntax.tab.h",
+    ],
+    cmd = "M4=$(M4) $(BISON) " +
+          "--output=$(location syntax.tab.cpp) " +
+          "--defines=$(location syntax.tab.h) " +
+          "$(location syntax.ypp)",
+    toolchains = [
+        "@rules_bison//bison:current_bison_toolchain",
+        "@rules_m4//m4:current_m4_toolchain",
+    ],
+)
+
+genrule(
+    name = "syntax_flex_srcs",
+    srcs = ["syntax.lpp"],
+    outs = ["syntax.yy.cpp"],
+    cmd = "M4=$(M4) $(FLEX) " +
+          "--outfile=$(location syntax.yy.cpp) " +
+          "$(location syntax.lpp)",
+    toolchains = [
+        "@rules_flex//flex:current_flex_toolchain",
+        "@rules_m4//m4:current_m4_toolchain",
+    ],
+)
diff --git a/executable_semantics/syntax.lpp b/executable_semantics/syntax/syntax.lpp
similarity index 97%
rename from executable_semantics/syntax.lpp
rename to executable_semantics/syntax/syntax.lpp
index 3807195c78e9..e1a934da97cb 100644
--- a/executable_semantics/syntax.lpp
+++ b/executable_semantics/syntax/syntax.lpp
@@ -6,7 +6,7 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 %{
 #include <cstdlib>
-#include "executable_semantics/syntax.tab.h"
+#include "executable_semantics/syntax/syntax.tab.h"
 %}
 
 /* Turn off legacy bits we don't need */
diff --git a/executable_semantics/syntax.ypp b/executable_semantics/syntax/syntax.ypp
similarity index 99%
rename from executable_semantics/syntax.ypp
rename to executable_semantics/syntax/syntax.ypp
index 4bb95de2969b..5f8a0105e86c 100644
--- a/executable_semantics/syntax.ypp
+++ b/executable_semantics/syntax/syntax.ypp
@@ -10,7 +10,7 @@
 #include <iostream>
 #include <list>
 
-#include "executable_semantics/syntax_helpers.h"
+#include "executable_semantics/syntax/syntax_helpers.h"
 }
 
 %code requires {
diff --git a/executable_semantics/syntax_helpers.cpp b/executable_semantics/syntax/syntax_helpers.cpp
similarity index 96%
rename from executable_semantics/syntax_helpers.cpp
rename to executable_semantics/syntax/syntax_helpers.cpp
index 06ff0cb543f0..fc8a9c129e0b 100644
--- a/executable_semantics/syntax_helpers.cpp
+++ b/executable_semantics/syntax/syntax_helpers.cpp
@@ -2,7 +2,7 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-#include "executable_semantics/syntax_helpers.h"
+#include "executable_semantics/syntax/syntax_helpers.h"
 
 #include <iostream>
 
diff --git a/executable_semantics/syntax_helpers.h b/executable_semantics/syntax/syntax_helpers.h
similarity index 100%
rename from executable_semantics/syntax_helpers.h
rename to executable_semantics/syntax/syntax_helpers.h