diff --git a/tools/update_whatsnew.py b/tools/update_whatsnew.py
new file mode 100644
index 0000000..4d3a82d
--- /dev/null
+++ b/tools/update_whatsnew.py
@@ -0,0 +1,74 @@
+"""Update the What's New doc (development version)
+
+This collects the snippets from whatsnew/pr/, moves their content into
+whatsnew/development.rst (chronologically ordered), and deletes the snippets.
+"""
+
+import io
+import os
+from os.path import dirname, basename, abspath, join as pjoin
+from subprocess import check_call, check_output
+
+repo_root = dirname(dirname(abspath(__file__)))
+whatsnew_dir = pjoin(repo_root, 'docs', 'source', 'whatsnew')
+pr_dir = pjoin(whatsnew_dir, 'pr')
+target = pjoin(whatsnew_dir, 'development.rst')
+
+FEATURE_MARK = ".. DO NOT EDIT THIS LINE BEFORE RELEASE. FEATURE INSERTION POINT."
+INCOMPAT_MARK = ".. DO NOT EDIT THIS LINE BEFORE RELEASE. INCOMPAT INSERTION POINT."
+
+# 1. Collect the whatsnew snippet files ---------------------------------------
+
+files = set(os.listdir(pr_dir))
+# Ignore explanatory and example files
+files.difference_update({'README.md',
+                         'incompat-switching-to-perl.rst',
+                         'antigravity-feature.rst'}
+                        )
+
+# Absolute paths
+files = {pjoin(pr_dir, f) for f in files}
+
+def getmtime(f):
+    return check_output(['git', 'log', '-1', '--format="%ai"', '--', f])
+
+files = sorted(files, key=getmtime)
+
+features, incompats = [], []
+for path in files:
+    with io.open(path, encoding='utf-8') as f:
+        content = f.read().rstrip()
+    if basename(path).startswith('incompat-'):
+        incompats.append(content)
+    else:
+        features.append(content)
+
+# Put the insertion markers back on the end, so they're ready for next time.
+feature_block = '\n\n'.join(features + [FEATURE_MARK])
+incompat_block = '\n\n'.join(incompats + [INCOMPAT_MARK])
+
+# 2. Update the target file ---------------------------------------------------
+
+with io.open(target, encoding='utf-8') as f:
+    content = f.read()
+
+assert content.count(FEATURE_MARK) == 1
+assert content.count(INCOMPAT_MARK) == 1
+
+content = content.replace(FEATURE_MARK, feature_block)
+content = content.replace(INCOMPAT_MARK, incompat_block)
+
+# Clean trailing whitespace
+content = '\n'.join(l.rstrip() for l in content.splitlines())
+
+with io.open(target, 'w', encoding='utf-8') as f:
+    f.write(content)
+
+# 3. Stage the changes in git -------------------------------------------------
+
+for file in files:
+    check_call(['git', 'rm', file])
+
+check_call(['git', 'add', target])
+
+print("Merged what's new changes. Check the diff and commit the change.")
\ No newline at end of file