diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8954742c146..6ec156cb321 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,7 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
-## Unreleased
+## [5.21.0] - 2024-04-17
 
 ### Updated
 - Updated Plotly.js from version 2.30.0 to version 2.31.1. See the [plotly.js CHANGELOG](https://github.com/plotly/plotly.js/blob/master/CHANGELOG.md#2311----2024-04-15) for more information. These changes are reflected in the auto-generated `plotly.graph_objects` module. Notable changes include:
@@ -13,6 +13,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   - Add "raw" `sizemode` to cone trace [[#6938](https://github.com/plotly/plotly.js/pull/6938)]
   - Add `layout.hoversubplots` to enable hover effects across multiple cartesian suplots sharing one axis [[#6947](https://github.com/plotly/plotly.js/pull/6947), [#6950](https://github.com/plotly/plotly.js/pull/6950)]
 
+### Fixed
+- Fixed `orjson` loading issue [[#4562](https://github.com/plotly/plotly.py/pull/4562)]
+
 ## [5.20.0] - 2024-03-13
 
 ### Updated
diff --git a/README.md b/README.md
index b1dd1248063..0699a2ad337 100644
--- a/README.md
+++ b/README.md
@@ -33,7 +33,7 @@
 
 ## Quickstart
 
-`pip install plotly==5.20.0`
+`pip install plotly==5.21.0`
 
 Inside [Jupyter](https://jupyter.org/install) (installable with `pip install "jupyterlab>=3" "ipywidgets>=7.6"`):
 
@@ -78,13 +78,13 @@ Built on top of [plotly.js](https://github.com/plotly/plotly.js), `plotly.py` is
 plotly.py may be installed using pip...
 
 ```
-pip install plotly==5.20.0
+pip install plotly==5.21.0
 ```
 
 or conda.
 
 ```
-conda install -c plotly plotly=5.20.0
+conda install -c plotly plotly=5.21.0
 ```
 
 ### JupyterLab Support
@@ -106,7 +106,7 @@ The instructions above apply to JupyterLab 3.x. **For JupyterLab 2 or earlier**,
 
 ```
 # JupyterLab 2.x renderer support
-jupyter labextension install jupyterlab-plotly@5.20.0 @jupyter-widgets/jupyterlab-manager
+jupyter labextension install jupyterlab-plotly@5.21.0 @jupyter-widgets/jupyterlab-manager
 ```
 
 Please check out our [Troubleshooting guide](https://plotly.com/python/troubleshooting/) if you run into any problems with JupyterLab.
diff --git a/packages/javascript/jupyterlab-plotly/package-lock.json b/packages/javascript/jupyterlab-plotly/package-lock.json
index 5b25cd7d9ad..c4ae1e2d9f0 100644
--- a/packages/javascript/jupyterlab-plotly/package-lock.json
+++ b/packages/javascript/jupyterlab-plotly/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "jupyterlab-plotly",
-  "version": "5.20.0",
+  "version": "5.21.0",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "jupyterlab-plotly",
-      "version": "5.20.0",
+      "version": "5.21.0",
       "license": "MIT",
       "dependencies": {
         "@jupyter-widgets/base": ">=2.0.0 <7.0.0",
diff --git a/packages/javascript/jupyterlab-plotly/package.json b/packages/javascript/jupyterlab-plotly/package.json
index 726753acc97..762986eb4e2 100644
--- a/packages/javascript/jupyterlab-plotly/package.json
+++ b/packages/javascript/jupyterlab-plotly/package.json
@@ -1,6 +1,6 @@
 {
   "name": "jupyterlab-plotly",
-  "version": "5.20.0",
+  "version": "5.21.0",
   "description": "The plotly Jupyter extension",
   "author": "The plotly.py team",
   "license": "MIT",
diff --git a/packages/python/plotly/plotly/_widget_version.py b/packages/python/plotly/plotly/_widget_version.py
index 571d738d478..1a869a98fd1 100644
--- a/packages/python/plotly/plotly/_widget_version.py
+++ b/packages/python/plotly/plotly/_widget_version.py
@@ -2,4 +2,4 @@
 # for automated dev builds
 #
 # It is edited by hand prior to official releases
-__frontend_version__ = "^5.20.0"
+__frontend_version__ = "^5.21.0"