diff --git a/.circleci/config.yml b/.circleci/config.yml
index 86becb42632..31fa793a9bc 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -22,7 +22,7 @@ jobs:
           command: |
               sudo apt update
               sudo apt install texlive texlive-latex-extra texlive-fonts-recommended dvipng cm-super
-              pip install pip tox --upgrade
+              pip install pip "tox<4"
       - run:
           name: Run tests
           command: tox -v
@@ -58,7 +58,7 @@ jobs:
           command: |
               sudo apt update
               sudo apt install texlive texlive-latex-extra texlive-fonts-recommended dvipng cm-super
-              pip install pip tox --upgrade
+              pip install pip "tox<4"
       - run: ssh-add -D
       - add_ssh_keys:
           fingerprints: "bf:aa:ef:e3:8d:95:11:0b:75:c7:92:52:ba:fb:e0:fc"
diff --git a/.github/workflows/ci_cron_daily.yml b/.github/workflows/ci_cron_daily.yml
index 0f0c182518b..f1791fc9d43 100644
--- a/.github/workflows/ci_cron_daily.yml
+++ b/.github/workflows/ci_cron_daily.yml
@@ -67,6 +67,6 @@ jobs:
         sudo apt-get update
         sudo apt-get install language-pack-de tzdata
     - name: Install Python dependencies
-      run: python -m pip install --upgrade tox
+      run: python -m pip install "tox<4"
     - name: Run tests
       run: tox ${{ matrix.toxargs}} -e ${{ matrix.toxenv}} -- ${{ matrix.toxposargs}}
diff --git a/.github/workflows/ci_cron_weekly.yml b/.github/workflows/ci_cron_weekly.yml
index 13d41424ef3..98e683681a9 100644
--- a/.github/workflows/ci_cron_weekly.yml
+++ b/.github/workflows/ci_cron_weekly.yml
@@ -83,7 +83,7 @@ jobs:
       if: ${{ matrix.toxenv == 'linkcheck' }}
       run: sudo apt-get install graphviz
     - name: Install Python dependencies
-      run: python -m pip install --upgrade tox
+      run: python -m pip install "tox<4"
     - name: Run tests
       run: tox ${{ matrix.toxargs}} -e ${{ matrix.toxenv}} -- ${{ matrix.toxposargs}}
 
diff --git a/.github/workflows/ci_workflows.yml b/.github/workflows/ci_workflows.yml
index ac009fd1759..0d3220d6e6d 100644
--- a/.github/workflows/ci_workflows.yml
+++ b/.github/workflows/ci_workflows.yml
@@ -102,7 +102,7 @@ jobs:
         sudo apt-get update
         sudo apt-get install language-pack-fr tzdata libopenblas-dev
     - name: Install tox
-      run: python -m pip install --upgrade tox
+      run: python -m pip install "tox<4"
     - name: Run tests
       run: tox ${{ matrix.toxargs }} -e ${{ matrix.toxenv }} -- ${{ matrix.toxposargs }}
     # TODO: Do we need --gcov-glob "*cextern*" ?
@@ -142,7 +142,7 @@ jobs:
         sudo apt-get update
         sudo apt-get install language-pack-de tzdata
     - name: Install Python dependencies
-      run: python -m pip install --upgrade tox
+      run: python -m pip install "tox<4"
     - name: Run tests
       run: tox ${{ matrix.toxargs }} -e ${{ matrix.toxenv }} -- ${{ matrix.toxposargs }}
 
@@ -166,7 +166,7 @@ jobs:
     # test the ability to run the test suite in parallel.
     # Numpy is pinned to avoid building it from source for numpy 1.21.5
     - name: Install dependencies for Python 3.8
-      run: /opt/python/cp38-cp38/bin/pip install tox
+      run: /opt/python/cp38-cp38/bin/pip install "tox<4"
     - name: Run tests for Python 3.8
       run: /opt/python/cp38-cp38/bin/python -m tox -e py38-numpy120-test -- -n=4 --durations=50
     # We use the 3.8 build to check that running tests twice in a row in the
diff --git a/tox.ini b/tox.ini
index 581ff633b64..e428b6be4f7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,6 +8,7 @@ requires =
     setuptools >= 30.3.0
     pip >= 19.3.1
     tox-pypi-filter >= 0.12
+    tox < 4
 isolated_build = true
 
 [testenv]