diff --git a/doc/godebug.md b/doc/godebug.md
index 1b5674f2cd0b5b..cdc09ddcc4792d 100644
--- a/doc/godebug.md
+++ b/doc/godebug.md
@@ -153,6 +153,17 @@ and the [go command documentation](/cmd/go#hdr-Build_and_test_caching).
 
 ### Go 1.24
 
+Go 1.24 added a new `fips140` setting that controls whether the Go
+Cryptographic Module operates in FIPS 140-3 mode.
+The possible values are:
+- "off": no special support for FIPS 140-3 mode. This is the default.
+- "on": the Go Cryptographic Module operates in FIPS 140-3 mode.
+- "only": like "on", but cryptographic algorithms not approved by
+  FIPS 140-3 return an error or panic.
+For more information, see [FIPS 140-3 Compliance](/doc/security/fips140).
+This setting is fixed at program startup time, and can't be modified
+by changing the `GODEBUG` environment variable after the program starts.
+
 Go 1.24 changed the global [`math/rand.Seed`](/pkg/math/rand/#Seed) to be a
 no-op. This behavior is controlled by the `randseednop` setting.
 For Go 1.24 it defaults to `randseednop=1`.