diff --git a/CHANGELOG.md b/CHANGELOG.md
index 14c703554..c647f9a39 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -48,6 +48,7 @@ and this project does not currently adhere to a particular versioning scheme.
 - Add local definitions to functional syntax.
 - Add repeated field name error message.
 - Add `Math` builtin functions. ([#570][gh-570])
+- Add primitive file IO function `IO/FS/flush`. ([#598][gh-598])
 
 ## [0.2.35] - 2024-06-06
 
@@ -387,3 +388,4 @@ and this project does not currently adhere to a particular versioning scheme.
 [gh-514]: https://github.com/HigherOrderCO/Bend/issues/514
 [gh-544]: https://github.com/HigherOrderCO/Bend/pull/544
 [Unreleased]: https://github.com/HigherOrderCO/Bend/compare/0.2.36...HEAD
+[gh-598]: https://github.com/HigherOrderCO/Bend/issues/598
diff --git a/docs/builtins.md b/docs/builtins.md
index 07ac88951..f15291dbf 100644
--- a/docs/builtins.md
+++ b/docs/builtins.md
@@ -429,6 +429,16 @@ Moves the current position of the file with the given `file` descriptor to the g
 
 Returns nothing (`*`).
 
+#### File flush
+
+```python
+def IO/FS/flush(file)
+```
+
+Flushes the file with the given `file` descriptor.
+
+Returns nothing (`*`).
+
 ## Numeric operations
 
 ### log
diff --git a/src/fun/builtins.bend b/src/fun/builtins.bend
index b89f6bd97..cbae7c78a 100644
--- a/src/fun/builtins.bend
+++ b/src/fun/builtins.bend
@@ -128,6 +128,7 @@ IO/FS/close file = (IO/Call IO/MAGIC "CLOSE" file @x (IO/Done IO/MAGIC x))
 IO/FS/read file num_bytes = (IO/Call IO/MAGIC "READ" (file, num_bytes) @x (IO/Done IO/MAGIC x))
 IO/FS/write file bytes = (IO/Call IO/MAGIC "WRITE" (file, bytes) @x (IO/Done IO/MAGIC x))
 IO/FS/seek file offset mode = (IO/Call IO/MAGIC "SEEK" (file, (offset, mode)) @x (IO/Done IO/MAGIC x))
+IO/FS/flush file = (IO/Call IO/MAGIC "FLUSH" file @x (IO/Done IO/MAGIC x))
 
 ### Always available files
 IO/FS/STDIN = 0