diff --git a/rhodecode/apps/admin/tests/test_admin_settings.py b/rhodecode/apps/admin/tests/test_admin_settings.py
--- a/rhodecode/apps/admin/tests/test_admin_settings.py
+++ b/rhodecode/apps/admin/tests/test_admin_settings.py
@@ -255,23 +255,6 @@ class TestAdminSettingsVcs(object):
                 'csrf_token': csrf_token},
             status=404)
 
-    def test_extensions_hgsubversion(self, form_defaults, csrf_token):
-        form_defaults.update({
-            'csrf_token': csrf_token,
-            'extensions_hgsubversion': 'True',
-        })
-        response = self.app.post(
-            route_path('admin_settings_vcs_update'),
-            params=form_defaults,
-            status=302)
-
-        response = response.follow()
-        extensions_input = (
-            '<input id="extensions_hgsubversion" '
-            'name="extensions_hgsubversion" type="checkbox" '
-            'value="True" checked="checked" />')
-        response.mustcontain(extensions_input)
-
     def test_extensions_hgevolve(self, form_defaults, csrf_token):
         form_defaults.update({
             'csrf_token': csrf_token,
diff --git a/rhodecode/lib/db_manage.py b/rhodecode/lib/db_manage.py
--- a/rhodecode/lib/db_manage.py
+++ b/rhodecode/lib/db_manage.py
@@ -378,14 +378,6 @@ class DbManage(object):
 
         self.sa.add(lfsstore)
 
-        # enable hgsubversion disabled by default
-        hgsubversion = RhodeCodeUi()
-        hgsubversion.ui_section = 'extensions'
-        hgsubversion.ui_key = 'hgsubversion'
-        hgsubversion.ui_value = ''
-        hgsubversion.ui_active = False
-        self.sa.add(hgsubversion)
-
         # enable hgevolve disabled by default
         hgevolve = RhodeCodeUi()
         hgevolve.ui_section = 'extensions'
diff --git a/rhodecode/lib/vcs/backends/base.py b/rhodecode/lib/vcs/backends/base.py
--- a/rhodecode/lib/vcs/backends/base.py
+++ b/rhodecode/lib/vcs/backends/base.py
@@ -1842,6 +1842,11 @@ class Config(object):
     def clear_section(self, section):
         self._values[section] = {}
 
+    def drop_option(self, section, option):
+        if section not in self._values:
+            raise ValueError(f'Section {section} does not exist')
+        del self._values[section][option]
+
     def serialize(self):
         """
         Creates a list of three tuples (section, key, value) representing
diff --git a/rhodecode/lib/vcs/backends/hg/repository.py b/rhodecode/lib/vcs/backends/hg/repository.py
--- a/rhodecode/lib/vcs/backends/hg/repository.py
+++ b/rhodecode/lib/vcs/backends/hg/repository.py
@@ -79,6 +79,13 @@ class MercurialRepository(BaseRepository
         # special requirements
         self.config = config if config else self.get_default_config(
             default=[('extensions', 'largefiles', '')])
+
+        # NOTE(marcink): since python3 hgsubversion is deprecated.
+        # From old installations we might still have this set enabled
+        # we explicitly remove this now here to make sure it wont propagate further
+        if config.get('extensions', 'hgsubversion') is not None:
+            config.drop_option('extensions', 'hgsubversion')
+
         self.with_wire = with_wire or {"cache": False}  # default should not use cache
 
         self._init_repo(create, src_url, do_workspace_checkout)
diff --git a/rhodecode/model/forms.py b/rhodecode/model/forms.py
--- a/rhodecode/model/forms.py
+++ b/rhodecode/model/forms.py
@@ -444,7 +444,6 @@ def ApplicationUiSettingsForm(localizer)
         vcs_git_lfs_store_location = All(
             v.ValidPath(localizer),
             v.UnicodeString(strip=True, min=2, not_empty=True))
-        extensions_hgsubversion = v.StringBoolean(if_missing=False)
         extensions_hggit = v.StringBoolean(if_missing=False)
         new_svn_branch = v.ValidSvnPattern(localizer, section='vcs_svn_branch')
         new_svn_tag = v.ValidSvnPattern(localizer, section='vcs_svn_tag')
diff --git a/rhodecode/model/settings.py b/rhodecode/model/settings.py
--- a/rhodecode/model/settings.py
+++ b/rhodecode/model/settings.py
@@ -488,7 +488,6 @@ class VcsSettingsModel(object):
         ('extensions', 'largefiles'),
         ('largefiles', 'usercache'),
         ('phases', 'publish'),
-        ('extensions', 'hgsubversion'),
         ('extensions', 'evolve'),
         ('extensions', 'topic'),
         ('experimental', 'evolution'),
@@ -672,10 +671,11 @@ class VcsSettingsModel(object):
             self.repo_settings, *phases, value=safe_str(data[phases_key]))
 
     def create_or_update_global_hg_settings(self, data):
-        largefiles, largefiles_store, phases, hgsubversion, evolve \
-            = self.GLOBAL_HG_SETTINGS[:5]
-        largefiles_key, largefiles_store_key, phases_key, subversion_key, evolve_key \
-            = self._get_settings_keys(self.GLOBAL_HG_SETTINGS[:5], data)
+        opts_len = 4
+        largefiles, largefiles_store, phases, evolve \
+            = self.GLOBAL_HG_SETTINGS[:opts_len]
+        largefiles_key, largefiles_store_key, phases_key, evolve_key \
+            = self._get_settings_keys(self.GLOBAL_HG_SETTINGS[:opts_len], data)
 
         self._create_or_update_ui(
             self.global_settings, *largefiles, value='',
@@ -685,8 +685,6 @@ class VcsSettingsModel(object):
         self._create_or_update_ui(
             self.global_settings, *phases, value=safe_str(data[phases_key]))
         self._create_or_update_ui(
-            self.global_settings, *hgsubversion, active=data[subversion_key])
-        self._create_or_update_ui(
             self.global_settings, *evolve, value='',
             active=data[evolve_key])
         self._set_evolution(self.global_settings, is_enabled=data[evolve_key])
diff --git a/rhodecode/templates/base/vcs_settings.mako b/rhodecode/templates/base/vcs_settings.mako
--- a/rhodecode/templates/base/vcs_settings.mako
+++ b/rhodecode/templates/base/vcs_settings.mako
@@ -121,15 +121,6 @@
                 <div class="label">
                     <span class="help-block">${_('When this is enabled all commits in the repository are seen as public commits by clients.')}</span>
                 </div>
-                % if display_globals:
-                    <div class="checkbox">
-                        ${h.checkbox('extensions_hgsubversion' + suffix,'True')}
-                        <label for="extensions_hgsubversion${suffix}">${_('Enable hgsubversion extension')}</label>
-                    </div>
-                    <div class="label">
-                        <span class="help-block">${_('Requires hgsubversion library to be installed. Allows cloning remote SVN repositories and migrates them to Mercurial type.')}</span>
-                    </div>
-                % endif
 
                 <div class="checkbox">
                     ${h.checkbox('extensions_evolve' + suffix, 'True', **kwargs)}
diff --git a/rhodecode/tests/models/settings/test_vcs_settings.py b/rhodecode/tests/models/settings/test_vcs_settings.py
--- a/rhodecode/tests/models/settings/test_vcs_settings.py
+++ b/rhodecode/tests/models/settings/test_vcs_settings.py
@@ -605,7 +605,6 @@ class TestCreateOrUpdateGlobalHgSettings
         'extensions_largefiles': False,
         'largefiles_usercache': '/example/largefiles-store',
         'phases_publish': False,
-        'extensions_hgsubversion': False,
         'extensions_evolve': False
     }
 
@@ -619,7 +618,6 @@ class TestCreateOrUpdateGlobalHgSettings
             mock.call(model.global_settings, 'extensions', 'largefiles', active=False, value=''),
             mock.call(model.global_settings, 'largefiles', 'usercache', value='/example/largefiles-store'),
             mock.call(model.global_settings, 'phases', 'publish', value='False'),
-            mock.call(model.global_settings, 'extensions', 'hgsubversion', active=False),
             mock.call(model.global_settings, 'extensions', 'evolve', active=False, value=''),
             mock.call(model.global_settings, 'experimental', 'evolution', active=False, value=''),
             mock.call(model.global_settings, 'experimental', 'evolution.exchange', active=False, value='no'),