diff --git a/CHANGELOG.md b/CHANGELOG.md
index db44aa9..44f9b49 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ### Unreleased
 
+## [v1.9.0]
+
+**Release date: 2023-12-11**
+
 ### Python Versions
 
 * Removed Python 3.7 support ([#376])
@@ -1436,6 +1440,7 @@ There was no CHANGELOG file prior to this release, so I don't have much
 information about changes, except for
 [commit messages](../../commits/v0.2).
 
+[v1.9.0]: ../../releases/tag/v1.9.0
 [v1.8.1]: ../../releases/tag/v1.8.1
 [v1.8.0]: ../../releases/tag/v1.8.0
 [v1.7.0]: ../../releases/tag/v1.7.0
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e7d5bd0..e21d790 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -27,10 +27,10 @@ For bug requests, please provide the following, if possible:
   ```python
   >>> from delphin.__about__ import __version__
   >>> __version__  # distribution version
-  '1.8.1'
+  '1.9.0'
   >>> from delphin import mrs
   >>> mrs.__version__  # package version
-  '1.8.1'
+  '1.9.0'
   ```
 * Python version (e.g. 3.9, 3.10, etc.)
 
diff --git a/delphin/__about__.py b/delphin/__about__.py
index 1e83e44..1a7f8e1 100644
--- a/delphin/__about__.py
+++ b/delphin/__about__.py
@@ -3,7 +3,7 @@
 # the warehouse project:
 #   https://github.com/pypa/warehouse/blob/master/warehouse/__about__.py
 
-__version__ = '1.8.1'
+__version__ = '1.9.0'
 __version_info__ = __version__.replace('.', ' ').replace('-', ' ').split()
 
 __title__ = 'PyDelphin'