diff --git a/docs/releases/0.21.1.md b/docs/releases/0.21.1.md
new file mode 100644
index 0000000000..185e950999
--- /dev/null
+++ b/docs/releases/0.21.1.md
@@ -0,0 +1,16 @@
+# 0.21.1 - 2024-03-28
+
+This release should fix some of the installation issues when building the River wheel from scratch.
+
+## anomaly
+
+- Added `PredictiveAnomalyDetection`, a semi-supervised technique that employs a predictive model for anomaly detection.
+
+## drift
+
+- Added `FHDDM` drift detector.
+- Added a `iter_polars` function to iterate over the rows of a polars DataFrame.
+
+## neighbors
+
+- Simplified `neighbors.SWINN` to avoid recursion limit and pickling issues.
diff --git a/docs/releases/unreleased.md b/docs/releases/unreleased.md
index 8e93b1f3e4..5a4ae4fc03 100644
--- a/docs/releases/unreleased.md
+++ b/docs/releases/unreleased.md
@@ -1,20 +1,5 @@
-# 0.21.1 - 2024-03-28
-
-This release should fix some of the installation issues when building the River wheel from scratch.
-
-## anomaly
-
-- Added `PredictiveAnomalyDetection`, a semi-supervised technique that employs a predictive model for anomaly detection.
+# Unreleased
 
 ## cluster
 
 - Added `ODAC` (Online Divisive-Agglomerative Clustering) for clustering time series.
-
-## drift
-
-- Added `FHDDM` drift detector.
-- Added a `iter_polars` function to iterate over the rows of a polars DataFrame.
-
-## neighbors
-
-- Simplified `neighbors.SWINN` to avoid recursion limit and pickling issues.