diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 4888d2aa172..b7acf8266ce 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -163,7 +163,7 @@ jobs:
         php-version:
           - "8.0"
         postgres-version:
-          - "9.4"
+          - "10"
           - "13"
           - "14"
         include:
diff --git a/UPGRADE.md b/UPGRADE.md
index cd6cbf76a8f..d0038856c9c 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -8,6 +8,13 @@ awareness about deprecated code.
 
 # Upgrade to 4.0
 
+## BC BREAK: Removed active support for Postgres 9
+
+Postgres 9 is not actively supported anymore. The following classes have been merged into their respective parent class:
+
+* `Doctrine\DBAL\Platforms\PostgreSQL100Platform`
+* `Doctrine\DBAL\Platforms\Keywords\PostgreSQL100Keywords`
+
 ## BC BREAK: Removed Platform "commented type" API
 
 Since `Type::requiresSQLCommentTypeHint()` already allows determining whether a
diff --git a/psalm.xml.dist b/psalm.xml.dist
index 8df3c2d60e1..48f00adf6b0 100644
--- a/psalm.xml.dist
+++ b/psalm.xml.dist
@@ -46,11 +46,6 @@
                     is no longer supported.
                 -->
                 <file name="src/Tools/Console/ConsoleRunner.php"/>
-                <!--
-                    TODO: remove in 4.0.0
-                -->
-                <referencedClass name="Doctrine\DBAL\Platforms\Keywords\PostgreSQL100Keywords"/>
-                <referencedClass name="Doctrine\DBAL\Platforms\PostgreSQL100Platform"/>
             </errorLevel>
         </DeprecatedClass>
         <DeprecatedMethod>
diff --git a/src/Driver/AbstractPostgreSQLDriver.php b/src/Driver/AbstractPostgreSQLDriver.php
index 7ff59438799..2c38a22c813 100644
--- a/src/Driver/AbstractPostgreSQLDriver.php
+++ b/src/Driver/AbstractPostgreSQLDriver.php
@@ -8,16 +8,11 @@
 use Doctrine\DBAL\Driver;
 use Doctrine\DBAL\Driver\API\PostgreSQL\ExceptionConverter;
 use Doctrine\DBAL\Platforms\AbstractPlatform;
-use Doctrine\DBAL\Platforms\Exception\InvalidPlatformVersion;
-use Doctrine\DBAL\Platforms\PostgreSQL100Platform;
 use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
 use Doctrine\DBAL\Schema\PostgreSQLSchemaManager;
 use Doctrine\DBAL\ServerVersionProvider;
-use Doctrine\Deprecations\Deprecation;
 
 use function assert;
-use function preg_match;
-use function version_compare;
 
 /**
  * Abstract base implementation of the {@link Driver} interface for PostgreSQL based drivers.
@@ -26,31 +21,6 @@ abstract class AbstractPostgreSQLDriver implements Driver
 {
     public function getDatabasePlatform(ServerVersionProvider $versionProvider): PostgreSQLPlatform
     {
-        $version = $versionProvider->getServerVersion();
-
-        if (preg_match('/^(?P<major>\d+)(?:\.(?P<minor>\d+)(?:\.(?P<patch>\d+))?)?/', $version, $versionParts) === 0) {
-            throw InvalidPlatformVersion::new(
-                $version,
-                '<major_version>.<minor_version>.<patch_version>'
-            );
-        }
-
-        $majorVersion = $versionParts['major'];
-        $minorVersion = $versionParts['minor'] ?? 0;
-        $patchVersion = $versionParts['patch'] ?? 0;
-        $version      = $majorVersion . '.' . $minorVersion . '.' . $patchVersion;
-
-        if (version_compare($version, '10.0', '>=')) {
-            return new PostgreSQL100Platform();
-        }
-
-        Deprecation::trigger(
-            'doctrine/dbal',
-            'https://github.com/doctrine/dbal/pull/5060',
-            'PostgreSQL 9 support is deprecated and will be removed in DBAL 4.'
-                . ' Consider upgrading to Postgres 10 or later.'
-        );
-
         return new PostgreSQLPlatform();
     }
 
diff --git a/src/Platforms/Keywords/PostgreSQL100Keywords.php b/src/Platforms/Keywords/PostgreSQL100Keywords.php
deleted file mode 100644
index 9e1c533bedd..00000000000
--- a/src/Platforms/Keywords/PostgreSQL100Keywords.php
+++ /dev/null
@@ -1,18 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Doctrine\DBAL\Platforms\Keywords;
-
-/**
- * PostgreSQL 10.0 reserved keywords list.
- *
- * @deprecated Use {@link PostgreSQLKeywords} instead.
- */
-class PostgreSQL100Keywords extends PostgreSQLKeywords
-{
-    public function getName(): string
-    {
-        return 'PostgreSQL100';
-    }
-}
diff --git a/src/Platforms/PostgreSQL100Platform.php b/src/Platforms/PostgreSQL100Platform.php
deleted file mode 100644
index 47cc08f0856..00000000000
--- a/src/Platforms/PostgreSQL100Platform.php
+++ /dev/null
@@ -1,34 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Doctrine\DBAL\Platforms;
-
-use Doctrine\DBAL\Platforms\Keywords\KeywordList;
-use Doctrine\DBAL\Platforms\Keywords\PostgreSQL100Keywords;
-
-/**
- * Provides the behavior, features and SQL dialect of the PostgreSQL 10.0 database platform.
- *
- * @deprecated This class will be merged with {@see PostgreSQLPlatform} in 4.0 because support for Postgres
- *             releases prior to 10.0 will be dropped.
- */
-class PostgreSQL100Platform extends PostgreSQLPlatform
-{
-    protected function createReservedKeywordsList(): KeywordList
-    {
-        return new PostgreSQL100Keywords();
-    }
-
-    public function getListSequencesSQL(string $database): string
-    {
-        return 'SELECT sequence_name AS relname,
-                       sequence_schema AS schemaname,
-                       minimum_value AS min_value,
-                       increment AS increment_by
-                FROM   information_schema.sequences
-                WHERE  sequence_catalog = ' . $this->quoteStringLiteral($database) . "
-                AND    sequence_schema NOT LIKE 'pg\_%'
-                AND    sequence_schema != 'information_schema'";
-    }
-}
diff --git a/src/Platforms/PostgreSQLPlatform.php b/src/Platforms/PostgreSQLPlatform.php
index d141b18795b..5565779beb2 100644
--- a/src/Platforms/PostgreSQLPlatform.php
+++ b/src/Platforms/PostgreSQLPlatform.php
@@ -167,10 +167,13 @@ public function getListDatabasesSQL(): string
 
     public function getListSequencesSQL(string $database): string
     {
-        return "SELECT sequence_name AS relname,
-                       sequence_schema AS schemaname
+        return 'SELECT sequence_name AS relname,
+                       sequence_schema AS schemaname,
+                       minimum_value AS min_value,
+                       increment AS increment_by
                 FROM   information_schema.sequences
-                WHERE  sequence_schema NOT LIKE 'pg\_%'
+                WHERE  sequence_catalog = ' . $this->quoteStringLiteral($database) . "
+                AND    sequence_schema NOT LIKE 'pg\_%'
                 AND    sequence_schema != 'information_schema'";
     }
 
diff --git a/src/Schema/PostgreSQLSchemaManager.php b/src/Schema/PostgreSQLSchemaManager.php
index 2b2edb8fe66..dd62dc248ae 100644
--- a/src/Schema/PostgreSQLSchemaManager.php
+++ b/src/Schema/PostgreSQLSchemaManager.php
@@ -20,7 +20,6 @@
 use function preg_match;
 use function sprintf;
 use function str_replace;
-use function strpos;
 use function strtolower;
 use function trim;
 
@@ -328,21 +327,12 @@ protected function _getPortableTableColumnDefinition(array $tableColumn): Column
         switch ($dbType) {
             case 'smallint':
             case 'int2':
-                $tableColumn['default'] = $this->fixVersion94NegativeNumericDefaultValue($tableColumn['default']);
-                $length                 = null;
-                break;
-
             case 'int':
             case 'int4':
             case 'integer':
-                $tableColumn['default'] = $this->fixVersion94NegativeNumericDefaultValue($tableColumn['default']);
-                $length                 = null;
-                break;
-
             case 'bigint':
             case 'int8':
-                $tableColumn['default'] = $this->fixVersion94NegativeNumericDefaultValue($tableColumn['default']);
-                $length                 = null;
+                $length = null;
                 break;
 
             case 'bool':
@@ -378,8 +368,6 @@ protected function _getPortableTableColumnDefinition(array $tableColumn): Column
             case 'decimal':
             case 'money':
             case 'numeric':
-                $tableColumn['default'] = $this->fixVersion94NegativeNumericDefaultValue($tableColumn['default']);
-
                 if (
                     preg_match(
                         '([A-Za-z]+\(([0-9]+),([0-9]+)\))',
@@ -442,18 +430,6 @@ protected function _getPortableTableColumnDefinition(array $tableColumn): Column
         return $column;
     }
 
-    /**
-     * PostgreSQL 9.4 puts parentheses around negative numeric default values that need to be stripped eventually.
-     */
-    private function fixVersion94NegativeNumericDefaultValue(mixed $defaultValue): mixed
-    {
-        if ($defaultValue !== null && strpos($defaultValue, '(') === 0) {
-            return trim($defaultValue, '()');
-        }
-
-        return $defaultValue;
-    }
-
     /**
      * Parses a default value expression as given by PostgreSQL
      */
diff --git a/src/Tools/Console/Command/ReservedWordsCommand.php b/src/Tools/Console/Command/ReservedWordsCommand.php
index 21b6bbe6a09..a8102dad3a1 100644
--- a/src/Tools/Console/Command/ReservedWordsCommand.php
+++ b/src/Tools/Console/Command/ReservedWordsCommand.php
@@ -13,7 +13,6 @@
 use Doctrine\DBAL\Platforms\Keywords\MySQL80Keywords;
 use Doctrine\DBAL\Platforms\Keywords\MySQLKeywords;
 use Doctrine\DBAL\Platforms\Keywords\OracleKeywords;
-use Doctrine\DBAL\Platforms\Keywords\PostgreSQL100Keywords;
 use Doctrine\DBAL\Platforms\Keywords\PostgreSQLKeywords;
 use Doctrine\DBAL\Platforms\Keywords\ReservedKeywordsValidator;
 use Doctrine\DBAL\Platforms\Keywords\SQLiteKeywords;
@@ -53,7 +52,6 @@ public function __construct(ConnectionProvider $connectionProvider)
             'mysql80'    => new MySQL80Keywords(),
             'oracle'     => new OracleKeywords(),
             'pgsql'      => new PostgreSQLKeywords(),
-            'pgsql100'   => new PostgreSQL100Keywords(),
             'sqlite'     => new SQLiteKeywords(),
             'sqlserver'  => new SQLServerKeywords(),
         ];
@@ -103,7 +101,6 @@ protected function configure(): void
     * mysql80
     * oracle
     * pgsql
-    * pgsql100
     * sqlite
     * sqlserver
 EOT
diff --git a/tests/Driver/AbstractPostgreSQLDriverTest.php b/tests/Driver/AbstractPostgreSQLDriverTest.php
index 32ef4daa890..1fd50bd95ce 100644
--- a/tests/Driver/AbstractPostgreSQLDriverTest.php
+++ b/tests/Driver/AbstractPostgreSQLDriverTest.php
@@ -10,7 +10,6 @@
 use Doctrine\DBAL\Driver\API\ExceptionConverter;
 use Doctrine\DBAL\Driver\API\PostgreSQL;
 use Doctrine\DBAL\Platforms\AbstractPlatform;
-use Doctrine\DBAL\Platforms\PostgreSQL100Platform;
 use Doctrine\DBAL\Platforms\PostgreSQLPlatform;
 use Doctrine\DBAL\Schema\AbstractSchemaManager;
 use Doctrine\DBAL\Schema\PostgreSQLSchemaManager;
@@ -20,6 +19,11 @@
  */
 class AbstractPostgreSQLDriverTest extends AbstractDriverTest
 {
+    public function testThrowsExceptionOnCreatingDatabasePlatformsForInvalidVersion(): void
+    {
+        self::markTestSkipped('PostgreSQL drivers do not use server version to instantiate platform');
+    }
+
     protected function createDriver(): Driver
     {
         return $this->getMockForAbstractClass(AbstractPostgreSQLDriver::class);
@@ -49,10 +53,9 @@ protected function createExceptionConverter(): ExceptionConverter
     public static function platformVersionProvider(): array
     {
         return [
-            ['9.4', PostgreSQLPlatform::class],
-            ['9.4.0', PostgreSQLPlatform::class],
-            ['9.4.1', PostgreSQLPlatform::class],
-            ['10', PostgreSQL100Platform::class],
+            ['10.0', PostgreSQLPlatform::class],
+            ['11.0', PostgreSQLPlatform::class],
+            ['13.3', PostgreSQLPlatform::class],
         ];
     }
 }
diff --git a/tests/Platforms/PostgreSQL100PlatformTest.php b/tests/Platforms/PostgreSQL100PlatformTest.php
deleted file mode 100644
index b6b524769b9..00000000000
--- a/tests/Platforms/PostgreSQL100PlatformTest.php
+++ /dev/null
@@ -1,31 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Doctrine\DBAL\Tests\Platforms;
-
-use Doctrine\DBAL\Platforms\AbstractPlatform;
-use Doctrine\DBAL\Platforms\PostgreSQL100Platform;
-
-class PostgreSQL100PlatformTest extends PostgreSQLPlatformTest
-{
-    public function createPlatform(): AbstractPlatform
-    {
-        return new PostgreSQL100Platform();
-    }
-
-    public function testGetListSequencesSQL(): void
-    {
-        self::assertSame(
-            "SELECT sequence_name AS relname,
-                       sequence_schema AS schemaname,
-                       minimum_value AS min_value,
-                       increment AS increment_by
-                FROM   information_schema.sequences
-                WHERE  sequence_catalog = 'test_db'
-                AND    sequence_schema NOT LIKE 'pg\_%'
-                AND    sequence_schema != 'information_schema'",
-            $this->platform->getListSequencesSQL('test_db')
-        );
-    }
-}
diff --git a/tests/Platforms/PostgreSQLPlatformTest.php b/tests/Platforms/PostgreSQLPlatformTest.php
index 61b54e401e4..924bbe4fcab 100644
--- a/tests/Platforms/PostgreSQLPlatformTest.php
+++ b/tests/Platforms/PostgreSQLPlatformTest.php
@@ -1027,4 +1027,19 @@ public function testInitializesJsonTypeMapping(): void
         self::assertTrue($this->platform->hasDoctrineTypeMappingFor('jsonb'));
         self::assertEquals(Types::JSON, $this->platform->getDoctrineTypeMapping('jsonb'));
     }
+
+    public function testGetListSequencesSQL(): void
+    {
+        self::assertSame(
+            "SELECT sequence_name AS relname,
+                       sequence_schema AS schemaname,
+                       minimum_value AS min_value,
+                       increment AS increment_by
+                FROM   information_schema.sequences
+                WHERE  sequence_catalog = 'test_db'
+                AND    sequence_schema NOT LIKE 'pg\_%'
+                AND    sequence_schema != 'information_schema'",
+            $this->platform->getListSequencesSQL('test_db')
+        );
+    }
 }