diff --git a/src/librustdoc/Cargo.toml b/src/librustdoc/Cargo.toml
index e02cef235ae00..945b2a8e9a80e 100644
--- a/src/librustdoc/Cargo.toml
+++ b/src/librustdoc/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/src/rustdoc-json-types/Cargo.toml b/src/rustdoc-json-types/Cargo.toml
index a692f6f896da7..d60699efd36cb 100644
--- a/src/rustdoc-json-types/Cargo.toml
+++ b/src/rustdoc-json-types/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc-json-types"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/src/tools/rustdoc-themes/Cargo.toml b/src/tools/rustdoc-themes/Cargo.toml
index 4b2ad982a84fb..3d8c77d36d70d 100644
--- a/src/tools/rustdoc-themes/Cargo.toml
+++ b/src/tools/rustdoc-themes/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc-themes"
 version = "0.1.0"
-edition = "2018"
+edition = "2021"
 
 [[bin]]
 name = "rustdoc-themes"
diff --git a/src/tools/rustdoc/Cargo.toml b/src/tools/rustdoc/Cargo.toml
index 5625707b25a53..c4101f72cc2da 100644
--- a/src/tools/rustdoc/Cargo.toml
+++ b/src/tools/rustdoc/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustdoc-tool"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 # Cargo adds a number of paths to the dylib search path on windows, which results in
 # the wrong rustdoc being executed. To avoid the conflicting rustdocs, we name the "tool"
diff --git a/src/tools/tidy/src/edition.rs b/src/tools/tidy/src/edition.rs
index 283c43e325c05..e58b690194f64 100644
--- a/src/tools/tidy/src/edition.rs
+++ b/src/tools/tidy/src/edition.rs
@@ -1,10 +1,13 @@
-//! Tidy check to ensure that crate `edition` is '2018'
+//! Tidy check to ensure that crate `edition` is '2018' or '2021'.
 
 use std::path::Path;
 
-fn is_edition_2018(mut line: &str) -> bool {
+fn is_edition_2018_or_2021(mut line: &str) -> bool {
     line = line.trim();
-    line == "edition = \"2018\"" || line == "edition = \'2018\'"
+    line == "edition = \"2018\""
+        || line == "edition = \'2018\'"
+        || line == "edition = \"2021\""
+        || line == "edition = \'2021\'"
 }
 
 pub fn check(path: &Path, bad: &mut bool) {
@@ -17,11 +20,11 @@ pub fn check(path: &Path, bad: &mut bool) {
             if filename != "Cargo.toml" {
                 return;
             }
-            let has_edition = contents.lines().any(is_edition_2018);
+            let has_edition = contents.lines().any(is_edition_2018_or_2021);
             if !has_edition {
                 tidy_error!(
                     bad,
-                    "{} doesn't have `edition = \"2018\"` on a separate line",
+                    "{} doesn't have `edition = \"2018\"` or `edition = \"2021\"` on a separate line",
                     file.display()
                 );
             }