diff --git a/.zuul.d/jobs.yaml b/.zuul.d/jobs.yaml
index 3b11241a91..b4f7ddebe4 100644
--- a/.zuul.d/jobs.yaml
+++ b/.zuul.d/jobs.yaml
@@ -12,6 +12,17 @@
     vars:
       tox_envlist: babel
 
+- job:
+    name: requirements-tox-py39-check-uc
+    parent: openstack-tox-py39
+    description: |
+      Run test for requirements project.
+
+      Uses tox with the ``py39-check-uc`` environment.
+    files: ^upper-constraints.*txt$
+    vars:
+      tox_envlist: py39-check-uc
+
 - job:
     name: requirements-tox-py310-check-uc
     parent: openstack-tox-py310
@@ -53,6 +64,16 @@
     vars:
       tox_envlist: py313-check-uc
 
+- job:
+    name: requirements-tox-py39-check-uc-no-wheels
+    parent: requirements-tox-py39-check-uc
+    description: |
+      Run test for requirements project.
+
+      Uses tox with the ``py39-check-uc`` environment.
+      Does not use wheel mirror.
+    pre-run: playbooks/drop-wheel-mirror.yaml
+
 - job:
     name: requirements-tox-py310-check-uc-no-wheels
     parent: requirements-tox-py310-check-uc
diff --git a/.zuul.d/project.yaml b/.zuul.d/project.yaml
index 50632e9ea0..8da4557a6e 100644
--- a/.zuul.d/project.yaml
+++ b/.zuul.d/project.yaml
@@ -17,6 +17,7 @@
         - requirements-tox-babel
         - requirements-tox-bindep:
             voting: false
+        - requirements-tox-py39-check-uc
         - requirements-tox-py310-check-uc
         - requirements-tox-py311-check-uc
         - requirements-tox-py312-check-uc
@@ -83,6 +84,7 @@
         - openstack-tox-validate
         - requirements-check-self
         - requirements-tox-babel
+        - requirements-tox-py39-check-uc
         - requirements-tox-py310-check-uc
         - requirements-tox-py311-check-uc
         - requirements-tox-py312-check-uc
@@ -118,6 +120,7 @@
       jobs:
         - nova-ceph-multistore
         - nova-next
+        - requirements-tox-py39-check-uc-no-wheels
         - requirements-tox-py310-check-uc-no-wheels
         - requirements-tox-py311-check-uc-no-wheels
         - requirements-tox-py312-check-uc-no-wheels
diff --git a/setup.cfg b/setup.cfg
index 2316101795..975d1e9e97 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -16,6 +16,7 @@ classifier =
     Operating System :: MacOS :: MacOS X
     Programming Language :: Python
     Programming Language :: Python :: 3
+    Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
     Programming Language :: Python :: 3.12
diff --git a/tox.ini b/tox.ini
index a675a6b474..0daaa0b672 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,6 +12,13 @@ deps = -c{toxinidir}/upper-constraints.txt
 commands =
   stestr run {posargs}
 
+[testenv:py39-check-uc]
+allowlist_externals =
+  check-conflicts
+basepython = python3.9
+deps = -r{toxinidir}/upper-constraints.txt
+commands = check-conflicts {toxinidir}/upper-constraints.txt {toxinidir}/upper-constraints-xfails.txt
+
 [testenv:py310-check-uc]
 basepython = python3.10
 deps = -r{toxinidir}/upper-constraints.txt
@@ -42,7 +49,7 @@ description = Regenerates upper-constraints.txt
 # Generate needs an unconstrained install to get new dependencies
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = generate-constraints {posargs: -d denylist.txt -r global-requirements.txt -p python3.10 -p python3.11 -p python3.12 -p python3.13 > upper-constraints.txt}
+commands = generate-constraints {posargs: -d denylist.txt -r global-requirements.txt -p python3.9 -p python3.10 -p python3.11 -p python3.12 -p python3.13 > upper-constraints.txt}
 
 [testenv:validate]
 allowlist_externals =
diff --git a/upper-constraints.txt b/upper-constraints.txt
index 05232daff4..909dd1a83d 100644
--- a/upper-constraints.txt
+++ b/upper-constraints.txt
@@ -40,7 +40,8 @@ ntc_templates===7.8.0
 sphinxcontrib-nwdiag===2.0.0
 rbd-iscsi-client===0.1.8
 requests-aws===0.1.8
-alabaster===1.0.0
+alabaster===0.7.16;python_version=='3.9'
+alabaster===1.0.0;python_version>='3.10'
 multidict===6.4.3
 pbr===6.1.1
 munch===4.0.0
@@ -48,7 +49,8 @@ waiting===1.5.0
 attrs===25.3.0
 microversion-parse===2.0.0
 jwcrypto===1.5.6
-Pint===0.24.4
+Pint===0.23;python_version=='3.9'
+Pint===0.24.4;python_version>='3.10'
 oslo.i18n===6.5.1
 jsonpath-rw-ext===1.2.2
 python-mistralclient===5.4.0
@@ -88,7 +90,8 @@ python-vitrageclient===5.2.0
 py-pure-client===1.67.0
 krest===1.3.6
 psycopg2===2.9.10
-networkx===3.4.2
+networkx===3.2.1;python_version=='3.9'
+networkx===3.4.2;python_version>='3.10'
 cheroot===10.0.1
 XStatic-Angular===1.8.2.2
 types-requests===2.31.0.6
@@ -104,7 +107,8 @@ pyOpenSSL===24.2.1
 monasca-common===3.8.0
 hyperframe===6.1.0
 zeroconf===0.146.5
-scipy===1.15.2
+scipy===1.13.1;python_version=='3.9'
+scipy===1.15.2;python_version>='3.10'
 opentelemetry-exporter-otlp===1.32.1
 python-gnupg===0.5.4
 rsd-lib===1.2.0
@@ -146,6 +150,7 @@ vine===5.1.0
 taskflow===5.12.0
 arrow===1.3.0
 semantic-version===2.10.0
+async-timeout===5.0.1;python_version=='3.9'
 async-timeout===5.0.1;python_version=='3.10'
 virtualbmc===3.2.0
 SQLAlchemy===2.0.40
@@ -204,6 +209,7 @@ sphinxcontrib-jsmath===1.0.1
 python-novaclient===18.9.0
 pact===1.12.0
 bcrypt===4.0.1
+exceptiongroup===1.2.2;python_version=='3.9'
 exceptiongroup===1.2.2;python_version=='3.10'
 os-client-config===2.1.0
 XStatic-Angular-Gettext===2.4.1.0
@@ -237,7 +243,8 @@ XStatic-JQuery-Migrate===3.3.2.1
 pytest-html===4.1.1
 appdirs===1.4.4
 google-auth-httplib2===0.2.0
-daiquiri===3.3.0
+daiquiri===3.2.5.1;python_version=='3.9'
+daiquiri===3.3.0;python_version>='3.10'
 influxdb===5.3.2
 funcparserlib===2.0.0a0
 passlib===1.7.4
@@ -386,9 +393,11 @@ python-consul===1.1.0
 more-itertools===10.7.0
 seqdiag===3.0.0
 zc.lockfile===3.0.post1
-numpy===2.2.5
+numpy===2.0.0;python_version=='3.9'
+numpy===2.2.5;python_version>='3.10'
 msgpack===1.1.0
-Sphinx===8.1.3
+Sphinx===7.4.7;python_version=='3.9'
+Sphinx===8.1.3;python_version>='3.10'
 oslo.config===9.7.1
 openstackdocstheme===3.5.0
 osc-placement===4.6.0
@@ -418,6 +427,7 @@ api-object-schema===2.0.0
 blinker===1.9.0
 aenum===3.1.15
 WSME===0.12.1
+tomli===2.2.1;python_version=='3.9'
 tomli===2.2.1;python_version=='3.10'
 oslo.upgradecheck===2.5.0
 sherlock===0.4.1
@@ -561,7 +571,8 @@ sqlalchemy-filters===0.13.0
 sphinxcontrib-runcmd===0.2.0
 confspirator===0.3.0
 fasteners===0.19
-importlib_metadata===8.6.1
+importlib-metadata===6.2.1;python_version=='3.9'
+importlib-metadata===8.6.1;python_version>='3.10'
 sortedcontainers===2.4.0
 python-linstor===1.25.3
 filelock===3.18.0