diff --git a/src/Database/Adapter/MariaDB.php b/src/Database/Adapter/MariaDB.php
index 78a09bbe5..7b86d6d00 100644
--- a/src/Database/Adapter/MariaDB.php
+++ b/src/Database/Adapter/MariaDB.php
@@ -1050,6 +1050,11 @@ protected function decodePolygon(string $wkb): array
      */
     protected const array INVALID_GEOMETRY_ERRORS = [3037];
 
+    /**
+     * ER_REGEXP_ERROR, for a pattern PCRE cannot compile or run.
+     */
+    protected const array INVALID_REGEX_ERRORS = [1139];
+
     /** The session timeout last set, in milliseconds. */
     private int $appliedTimeout = 0;
 
@@ -1614,6 +1619,10 @@ protected function processException(PDOException $e): Exception
             return new LimitException('Value is out of range', $e->getCode(), $e);
         }
 
+        if (isset($e->errorInfo[1]) && \in_array($e->errorInfo[1], static::INVALID_REGEX_ERRORS, true)) {
+            return new QueryException('Invalid regular expression', $e->getCode(), $e);
+        }
+
         if (isset($e->errorInfo[1]) && \in_array($e->errorInfo[1], static::INVALID_GEOMETRY_ERRORS, true)) {
             return new QueryException('Invalid spatial value', $e->getCode(), $e);
         }
diff --git a/src/Database/Adapter/Memory.php b/src/Database/Adapter/Memory.php
index d44e929f4..8ba136a0c 100644
--- a/src/Database/Adapter/Memory.php
+++ b/src/Database/Adapter/Memory.php
@@ -13,6 +13,7 @@
 use Utopia\Database\Exception\Limit as LimitException;
 use Utopia\Database\Exception\NotFound as NotFoundException;
 use Utopia\Database\Exception\Operator as OperatorException;
+use Utopia\Database\Exception\Query as QueryException;
 use Utopia\Database\Exception\Unique as UniqueException;
 use Utopia\Database\Index;
 use Utopia\Database\Operator;
@@ -2783,11 +2784,16 @@ protected function tokenize(string $text): array
      * Apply the supplied regex against $value. Pattern is the raw expression
      * — wrap it in delimiters before passing to preg_match, mirroring how
      * MariaDB's REGEXP operator accepts the pattern verbatim.
+     *
+     * @throws QueryException When the pattern does not compile
      */
     protected function matchesRegex(string $value, string $pattern): bool
     {
         $delimited = '#'.\str_replace('#', '\\#', $pattern).'#u';
         $matched = @\preg_match($delimited, $value);
+        if ($matched === false && \preg_last_error() === PREG_INTERNAL_ERROR) {
+            throw new QueryException('Invalid regular expression');
+        }
 
         return $matched === 1;
     }
diff --git a/src/Database/Adapter/Mongo.php b/src/Database/Adapter/Mongo.php
index afd8aeaf7..e43499183 100644
--- a/src/Database/Adapter/Mongo.php
+++ b/src/Database/Adapter/Mongo.php
@@ -3887,6 +3887,10 @@ protected function processException(Throwable $e): Throwable
             return new TypeException('Invalid operation', $e->getCode(), $e);
         }
 
+        if ($e->getCode() === 51091) {
+            return new QueryException('Invalid regular expression', $e->getCode(), $e);
+        }
+
         if ($e->getCode() === 28764) {
             return new LimitException('Value out of range', $e->getCode(), $e);
         }
diff --git a/src/Database/Adapter/MySQL.php b/src/Database/Adapter/MySQL.php
index 2350b8d0e..8a7a2fb91 100644
--- a/src/Database/Adapter/MySQL.php
+++ b/src/Database/Adapter/MySQL.php
@@ -122,6 +122,14 @@ protected function processException(PDOException $e): Exception
      */
     protected const array INVALID_GEOMETRY_ERRORS = [3037, 3616, 3617];
 
+    /**
+     * ER_REGEXP_ERROR, which MySQL raises for an error ICU only names, and the errors for a pattern ICU cannot compile
+     * or run: illegal argument, rule syntax, bad escape sequence, unimplemented, mismatched parenthesis, bad interval,
+     * max below min, invalid back reference, look-behind limit, missing close bracket, invalid range, stack overflow,
+     * pattern too big and invalid capture group name. ER_REGEXP_TIME_OUT is a timeout.
+     */
+    protected const array INVALID_REGEX_ERRORS = [1139, 3685, 3688, 3689, 3690, 3691, 3692, 3693, 3694, 3695, 3696, 3697, 3698, 3700, 3887];
+
     #[\Override]
     protected function dialectBuilder(): SQLBuilder&Scoping
     {
diff --git a/src/Database/Adapter/Postgres.php b/src/Database/Adapter/Postgres.php
index 70fbdf49e..24e3536e0 100644
--- a/src/Database/Adapter/Postgres.php
+++ b/src/Database/Adapter/Postgres.php
@@ -1946,6 +1946,10 @@ protected function processException(PDOException $e): Exception
             return new LimitException('Numeric value out of range', $e->getCode(), $e);
         }
 
+        if ($e->getCode() === '2201B' && isset($e->errorInfo[1]) && $e->errorInfo[1] === 7) {
+            return new QueryException('Invalid regular expression', $e->getCode(), $e);
+        }
+
         if ($e->getCode() === '2201F' && isset($e->errorInfo[1]) && $e->errorInfo[1] === 7) {
             return new LimitException('Invalid argument for power function', $e->getCode(), $e);
         }
diff --git a/src/Database/Adapter/Redis.php b/src/Database/Adapter/Redis.php
index efcc16259..429dc767a 100644
--- a/src/Database/Adapter/Redis.php
+++ b/src/Database/Adapter/Redis.php
@@ -3109,8 +3109,12 @@ private function matchesDocument(Document $document, Query $query): bool
                 }
                 $pattern = $this->stringOrEmpty($values[0] ?? '');
                 $delimited = '#'.\str_replace('#', '\\#', $pattern).'#u';
+                $matched = @\preg_match($delimited, $value);
+                if ($matched === false && \preg_last_error() === PREG_INTERNAL_ERROR) {
+                    throw new QueryException('Invalid regular expression');
+                }
 
-                return @\preg_match($delimited, $value) === 1;
+                return $matched === 1;
         }
 
         throw new QueryException('Query method not supported by Redis adapter: '.$method->value);
diff --git a/src/Database/Adapter/SQLite.php b/src/Database/Adapter/SQLite.php
index 238dbe27e..1922b4b75 100644
--- a/src/Database/Adapter/SQLite.php
+++ b/src/Database/Adapter/SQLite.php
@@ -271,19 +271,22 @@ private function registerUserFunctions(): void
             }
 
             if (!isset($delimitedCache[$pattern])) {
-                if (\count($delimitedCache) >= self::REGEXP_PATTERN_CACHE_LIMIT) {
-                    \array_shift($delimitedCache);
-                }
                 // Use a delimiter unlikely to appear in user input (chr(1))
                 // so we don't have to escape forward-slashes the user wrote
                 // intentionally and risk double-escaping backslashes.
-                $delimitedCache[$pattern] = "\x01" . $pattern . "\x01u";
+                $delimited = "\x01" . $pattern . "\x01u";
+                if (@\preg_match($delimited, '') === false && \preg_last_error() === PREG_INTERNAL_ERROR) {
+                    throw new QueryException('Invalid regular expression');
+                }
+                if (\count($delimitedCache) >= self::REGEXP_PATTERN_CACHE_LIMIT) {
+                    \array_shift($delimitedCache);
+                }
+                $delimitedCache[$pattern] = $delimited;
             }
             $delimited = $delimitedCache[$pattern];
 
-            // preg_match returns false on bad pattern / runtime error
-            // (e.g. PREG_BACKTRACK_LIMIT_ERROR). Silently treat those as
-            // no-match — REGEXP is a query predicate, not a validator.
+            // preg_match returns false on a runtime error such as
+            // PREG_BACKTRACK_LIMIT_ERROR, which reads as no match.
             $result = @\preg_match($delimited, $value);
 
             return $result === 1 ? 1 : 0;
diff --git a/tests/e2e/Adapter/Scopes/DocumentTests.php b/tests/e2e/Adapter/Scopes/DocumentTests.php
index bab056537..8cd3ffc45 100644
--- a/tests/e2e/Adapter/Scopes/DocumentTests.php
+++ b/tests/e2e/Adapter/Scopes/DocumentTests.php
@@ -4908,6 +4908,40 @@ public function testFindRegex(): void
         $database->deleteCollection('moviesRegex');
     }
 
+    /**
+     * A pattern the engine cannot compile failed as an unmapped PDOException on the SQL engines and a raw driver
+     * error on MongoDB, and matched nothing on SQLite, Memory and Redis. Every adapter refuses it as a query error.
+     */
+    public function testInvalidRegexIsAQueryError(): void
+    {
+        $database = $this->getDatabase();
+        $collection = 'invalid_regex_'.\substr(\uniqid(), -6);
+        $database->createCollection(Collection::create(
+            id: $collection,
+            attributes: [Attribute::string(key: 'text', size: 100, required: true)],
+            permissions: [Permission::create(Role::any()), Permission::read(Role::any())],
+        ));
+        $database->createDocument($collection, new Document([
+            'text' => 'target',
+            '$permissions' => [Permission::read(Role::any())],
+        ]));
+
+        foreach (['((', '[', 'a{2,1}', ')', '*a'] as $pattern) {
+            foreach (['find' => fn () => $database->find($collection, [Query::regex('text', $pattern)]), 'count' => fn () => $database->count($collection, [Query::regex('text', $pattern)])] as $read => $call) {
+                try {
+                    $call();
+                    $this->fail("{$read}() refuses the pattern {$pattern}");
+                } catch (QueryException $e) {
+                    $this->assertSame('Invalid regular expression', $e->getMessage(), "{$read}() of {$pattern}");
+                }
+            }
+        }
+
+        $this->assertCount(1, $database->find($collection, [Query::regex('text', '^tar')]));
+
+        $database->deleteCollection($collection);
+    }
+
     public function testRegexInjection(): void
     {
         /** @var Database $database */
diff --git a/tests/e2e/Adapter/Scopes/MongoReadFilterTests.php b/tests/e2e/Adapter/Scopes/MongoReadFilterTests.php
index 8ede7b8b2..ed4584c01 100644
--- a/tests/e2e/Adapter/Scopes/MongoReadFilterTests.php
+++ b/tests/e2e/Adapter/Scopes/MongoReadFilterTests.php
@@ -147,8 +147,10 @@ public function testCountReportsDriverErrors(): void
         try {
             $database->getAdapter()->count($database->getCollection($collection), [Query::regex('name', '(')]);
             $this->fail('count() must report the driver error for an invalid regular expression instead of 0');
-        } catch (MongoException $e) {
-            $this->assertNotSame(0, $e->getCode());
+        } catch (QueryException $e) {
+            $this->assertSame('Invalid regular expression', $e->getMessage());
+            $this->assertInstanceOf(MongoException::class, $e->getPrevious());
+            $this->assertNotSame(0, $e->getPrevious()->getCode());
         } finally {
             $database->deleteCollection($collection);
         }
diff --git a/tests/unit/EngineErrorMappingTest.php b/tests/unit/EngineErrorMappingTest.php
index 6ad0bf2cb..79f95cdb2 100644
--- a/tests/unit/EngineErrorMappingTest.php
+++ b/tests/unit/EngineErrorMappingTest.php
@@ -121,6 +121,28 @@ public static function invalidInputProvider(): iterable
         foreach ($geometries as $name => $error) {
             yield "MySQL {$name}" => [self::mySQL(), $error, 'Invalid spatial value'];
         }
+
+        yield 'MariaDB invalid regular expression' => [
+            self::mariaDB(),
+            self::engineError('42000', 1139, "SQLSTATE[42000]: Syntax error or access violation: 1139 Regex error 'missing closing parenthesis at offset 2'"),
+            'Invalid regular expression',
+        ];
+        $patterns = [
+            'mismatched parenthesis' => self::engineError('HY000', 3691, 'SQLSTATE[HY000]: General error: 3691 Mismatched parenthesis in regular expression.'),
+            'unclosed bracket' => self::engineError('HY000', 3696, 'SQLSTATE[HY000]: General error: 3696 The regular expression contains an unclosed bracket expression.'),
+            'interval maximum below minimum' => self::engineError('HY000', 3693, 'SQLSTATE[HY000]: General error: 3693 The maximum is less than the minumum in a {min,max} interval.'),
+            'syntax error' => self::engineError('HY000', 3688, 'SQLSTATE[HY000]: General error: 3688 Syntax error in regular expression on line 1, character 1.'),
+            'invalid capture group name' => self::engineError('HY000', 3887, 'SQLSTATE[HY000]: General error: 3887 A capture group has an invalid name.'),
+            'error ICU only names' => self::engineError('42000', 1139, "SQLSTATE[42000]: Syntax error or access violation: 1139 Got error 'U_ILLEGAL_CHAR_FOUND' from regexp"),
+        ];
+        foreach ($patterns as $name => $error) {
+            yield "MySQL {$name}" => [self::mySQL(), $error, 'Invalid regular expression'];
+        }
+        yield 'Postgres invalid regular expression' => [
+            self::postgres(),
+            self::engineError('2201B', 7, 'SQLSTATE[2201B]: Invalid regular expression: 7 ERROR:  invalid regular expression: parentheses () not balanced'),
+            'Invalid regular expression',
+        ];
     }
 
     /**
diff --git a/tests/unit/MemoryRegexTest.php b/tests/unit/MemoryRegexTest.php
new file mode 100644
index 000000000..8b7f180cc
--- /dev/null
+++ b/tests/unit/MemoryRegexTest.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+use Utopia\Cache\Adapter\None;
+use Utopia\Cache\Cache;
+use Utopia\Database\Adapter\Memory;
+use Utopia\Database\Attribute;
+use Utopia\Database\Collection;
+use Utopia\Database\Database;
+use Utopia\Database\Document;
+use Utopia\Database\Exception\Query as QueryException;
+use Utopia\Database\Permission;
+use Utopia\Database\Query;
+use Utopia\Database\Role;
+use Utopia\Database\Validator\Authorization;
+
+/**
+ * The Memory adapter matches a regex with PCRE, and refuses a pattern PCRE cannot compile as the engines do instead
+ * of reading it as matching nothing.
+ */
+final class MemoryRegexTest extends TestCase
+{
+    private const string COLLECTION = 'words';
+
+    private function database(): Database
+    {
+        $database = new Database(new Memory(), new Cache(new None()));
+        $database
+            ->setDatabase('regex')
+            ->setNamespace('regex')
+            ->setAuthorization(new Authorization());
+        $database->create();
+
+        $database->createCollection(Collection::create(
+            id: self::COLLECTION,
+            attributes: [Attribute::string('name', size: 32)],
+            permissions: [Permission::create(Role::any()), Permission::read(Role::any())],
+        ));
+        foreach (['abc', 'axc'] as $name) {
+            $database->createDocument(self::COLLECTION, new Document(['name' => $name]));
+        }
+
+        return $database;
+    }
+
+    public function testAPatternThatDoesNotCompileIsAQueryError(): void
+    {
+        $database = $this->database();
+
+        foreach (['((', '[', 'a{2,1}'] as $pattern) {
+            try {
+                $database->find(self::COLLECTION, [Query::regex('name', $pattern)]);
+                $this->fail("The pattern {$pattern} is refused");
+            } catch (QueryException $e) {
+                $this->assertSame('Invalid regular expression', $e->getMessage());
+            }
+        }
+    }
+
+    public function testAPatternThatCompilesStillMatches(): void
+    {
+        $this->assertCount(1, $this->database()->find(self::COLLECTION, [Query::regex('name', '^a[b]c$')]));
+    }
+}
diff --git a/tests/unit/SQLiteRegexTest.php b/tests/unit/SQLiteRegexTest.php
index b22acf5ae..48efce508 100644
--- a/tests/unit/SQLiteRegexTest.php
+++ b/tests/unit/SQLiteRegexTest.php
@@ -12,6 +12,7 @@
 use Utopia\Database\Collection;
 use Utopia\Database\Database;
 use Utopia\Database\Document;
+use Utopia\Database\Exception\Query as QueryException;
 use Utopia\Database\PDO as DatabasePDO;
 use Utopia\Database\Permission;
 use Utopia\Database\Query;
@@ -43,6 +44,20 @@ public function testRegexMatchesThroughTheUserFunction(): void
         $this->assertSame(3, $database->count(self::COLLECTION, [Query::regex('name', self::PATTERN)]));
     }
 
+    public function testAPatternThatDoesNotCompileIsAQueryError(): void
+    {
+        $database = $this->database();
+
+        foreach (['((', '[', 'a{2,1}'] as $pattern) {
+            try {
+                $database->find(self::COLLECTION, [Query::regex('name', $pattern)]);
+                $this->fail("The pattern {$pattern} is refused");
+            } catch (QueryException $e) {
+                $this->assertSame('Invalid regular expression', $e->getMessage());
+            }
+        }
+    }
+
     public function testRegexNeedsTheUserFunction(): void
     {
         $database = $this->database(new PDO('sqlite::memory:'));