diff --git a/lib/std/Io.zig b/lib/std/Io.zig
index 57999d8a2b3a42391ec2ab5cc3b93bf5ac89c3a6..b4d6efc715f163e0b59300d355284423d8b33382 100644
--- a/lib/std/Io.zig
+++ b/lib/std/Io.zig
@@ -1,3 +1,16 @@
+//! A cross-platform interface that abstracts all I/O operations and
+//! concurrency. It includes:
+//! * file system
+//! * networking
+//! * processes
+//! * time and sleeping
+//! * randomness
+//! * async, await, concurrent, and cancel
+//! * concurrent queues
+//! * wait groups and select
+//! * mutexes, futexes, events, and conditions
+//! This interface allows programmers to write optimal, reusable code while
+//! participating in these operations.
 const Io = @This();
 
 const builtin = @import("builtin");