diff --git a/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php b/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php
index 44531957d5b7..36436037e75f 100755
--- a/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php
+++ b/src/Illuminate/Database/Eloquent/Relations/MorphOneOrMany.php
@@ -4,6 +4,8 @@
 
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Schema\Builder as SchemaBuilder;
+use Illuminate\Support\Collection;
 use Illuminate\Support\Str;
 
 /**
@@ -53,16 +55,29 @@ public function __construct(Builder $query, Model $parent, $type, $id, $localKey
      *
      * @return void
      */
+    #[\Override]
     public function addConstraints()
     {
         if (static::$constraints) {
             $this->getRelationQuery()->where($this->morphType, $this->morphClass);
 
-            parent::addConstraints();
+            if (is_null(SchemaBuilder::$defaultMorphKeyType)) {
+                parent::addConstraints();
+            } else {
+                $query = $this->getRelationQuery();
+
+                $query->where($this->foreignKey, '=', transform($this->getParentKey(), fn ($key) => match (SchemaBuilder::$defaultMorphKeyType) {
+                    'uuid', 'ulid', 'string' => (string) $key,
+                    default => $key,
+                }));
+
+                $query->whereNotNull($this->foreignKey);
+            }
         }
     }
 
     /** @inheritDoc */
+    #[\Override]
     public function addEagerConstraints(array $models)
     {
         parent::addEagerConstraints($models);
@@ -113,6 +128,7 @@ protected function setForeignAttributesForCreate(Model $model)
      * @param  array|null  $update
      * @return int
      */
+    #[\Override]
     public function upsert(array $values, $uniqueBy, $update = null)
     {
         if (! empty($values) && ! is_array(reset($values))) {
@@ -127,6 +143,7 @@ public function upsert(array $values, $uniqueBy, $update = null)
     }
 
     /** @inheritDoc */
+    #[\Override]
     public function getRelationExistenceQuery(Builder $query, Builder $parentQuery, $columns = ['*'])
     {
         return parent::getRelationExistenceQuery($query, $parentQuery, $columns)->where(
@@ -176,4 +193,26 @@ protected function getPossibleInverseRelations(): array
             ...parent::getPossibleInverseRelations(),
         ]);
     }
+
+    /** @inheritDoc */
+    #[\Override]
+    protected function getKeys(array $models, $key = null)
+    {
+        $castKeyToString = in_array(SchemaBuilder::$defaultMorphKeyType, ['uuid', 'ulid', 'string']);
+
+        return (new Collection(parent::getKeys($models, $key)))
+            ->transform(fn ($key) => $castKeyToString === true ? (string) $key : $key)
+            ->all();
+    }
+
+    /** @inheritDoc */
+    #[\Override]
+    protected function whereInMethod(Model $model, $key)
+    {
+        if (! in_array(SchemaBuilder::$defaultMorphKeyType, ['uuid', 'ulid', 'string'])) {
+            return parent::whereInMethod($model, $key);
+        }
+
+        return 'whereIn';
+    }
 }
diff --git a/src/Illuminate/Database/Schema/Blueprint.php b/src/Illuminate/Database/Schema/Blueprint.php
index ca2eed4eb55b..603b2dedd657 100755
--- a/src/Illuminate/Database/Schema/Blueprint.php
+++ b/src/Illuminate/Database/Schema/Blueprint.php
@@ -1486,6 +1486,8 @@ public function morphs($name, $indexName = null)
             $this->uuidMorphs($name, $indexName);
         } elseif (Builder::$defaultMorphKeyType === 'ulid') {
             $this->ulidMorphs($name, $indexName);
+        } elseif (Builder::$defaultMorphKeyType === 'string') {
+            $this->stringableMorphs($name, $indexName);
         } else {
             $this->numericMorphs($name, $indexName);
         }
@@ -1504,11 +1506,45 @@ public function nullableMorphs($name, $indexName = null)
             $this->nullableUuidMorphs($name, $indexName);
         } elseif (Builder::$defaultMorphKeyType === 'ulid') {
             $this->nullableUlidMorphs($name, $indexName);
+        } elseif (Builder::$defaultMorphKeyType === 'string') {
+            $this->nullableStringableMorphs($name, $indexName);
         } else {
             $this->nullableNumericMorphs($name, $indexName);
         }
     }
 
+    /**
+     * Add the proper columns for a polymorphic table using string as IDs (mixed of UUID/ULID & incremental integer).
+     *
+     * @param  string  $name
+     * @param  string|null  $indexName
+     * @return void
+     */
+    public function stringableMorphs($name, $indexName = null)
+    {
+        $this->string("{$name}_type");
+
+        $this->string("{$name}_id");
+
+        $this->index(["{$name}_type", "{$name}_id"], $indexName);
+    }
+
+    /**
+     * Add nullable columns for a polymorphic table using string as IDs (mixed of UUID/ULID & incremental integer).
+     *
+     * @param  string  $name
+     * @param  string|null  $indexName
+     * @return void
+     */
+    public function nullableStringableMorphs($name, $indexName = null)
+    {
+        $this->string("{$name}_type")->nullable();
+
+        $this->string("{$name}_id")->nullable();
+
+        $this->index(["{$name}_type", "{$name}_id"], $indexName);
+    }
+
     /**
      * Add the proper columns for a polymorphic table using numeric IDs (incremental).
      *
diff --git a/src/Illuminate/Database/Schema/Builder.php b/src/Illuminate/Database/Schema/Builder.php
index 9af11e2e0836..bd1f2dcaab74 100755
--- a/src/Illuminate/Database/Schema/Builder.php
+++ b/src/Illuminate/Database/Schema/Builder.php
@@ -44,9 +44,9 @@ class Builder
     /**
      * The default relationship morph key type.
      *
-     * @var string
+     * @var string|null
      */
-    public static $defaultMorphKeyType = 'int';
+    public static $defaultMorphKeyType = null;
 
     /**
      * Create a new database Schema manager.
@@ -81,8 +81,8 @@ public static function defaultStringLength($length)
      */
     public static function defaultMorphKeyType(string $type)
     {
-        if (! in_array($type, ['int', 'uuid', 'ulid'])) {
-            throw new InvalidArgumentException("Morph key type must be 'int', 'uuid', or 'ulid'.");
+        if (! in_array($type, ['int', 'uuid', 'ulid', 'string'])) {
+            throw new InvalidArgumentException("Morph key type must be 'int', 'uuid', 'ulid', or 'string'.");
         }
 
         static::$defaultMorphKeyType = $type;
@@ -108,6 +108,16 @@ public static function morphUsingUlids()
         static::defaultMorphKeyType('ulid');
     }
 
+    /**
+     * Set the default morph key type for migrations to string as IDs (mixed of UUID/ULID & incremental integer).
+     *
+     * @return void
+     */
+    public static function morphUsingString()
+    {
+        static::defaultMorphKeyType('string');
+    }
+
     /**
      * Create a database in the schema.
      *
diff --git a/tests/Database/DatabaseSchemaBlueprintTest.php b/tests/Database/DatabaseSchemaBlueprintTest.php
index f92672b2f63e..b5a0facade8f 100755
--- a/tests/Database/DatabaseSchemaBlueprintTest.php
+++ b/tests/Database/DatabaseSchemaBlueprintTest.php
@@ -19,7 +19,7 @@ class DatabaseSchemaBlueprintTest extends TestCase
     protected function tearDown(): void
     {
         m::close();
-        Builder::$defaultMorphKeyType = 'int';
+        Builder::$defaultMorphKeyType = null;
     }
 
     public function testToSqlRunsCommandsFromBlueprint()
diff --git a/tests/Integration/Database/EloquentPolymorphicWithStringMorphTypeTest.php b/tests/Integration/Database/EloquentPolymorphicWithStringMorphTypeTest.php
new file mode 100644
index 000000000000..83bd71c41382
--- /dev/null
+++ b/tests/Integration/Database/EloquentPolymorphicWithStringMorphTypeTest.php
@@ -0,0 +1,110 @@
+<?php
+
+namespace Illuminate\Tests\Integration\Database;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Schema\Builder as SchemaBuilder;
+use Illuminate\Foundation\Auth\User as Authenticatable;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Testing\Assert;
+use Orchestra\Testbench\Attributes\WithMigration;
+use Orchestra\Testbench\Factories\UserFactory;
+
+#[WithMigration]
+class EloquentPolymorphicWithStringMorphTypeTest extends DatabaseTestCase
+{
+    /** @inheritDoc */
+    protected function setUp(): void
+    {
+        SchemaBuilder::morphUsingString();
+
+        parent::setUp();
+    }
+
+    /** @inheritDoc */
+    protected function tearDown(): void
+    {
+        parent::tearDown();
+
+        SchemaBuilder::$defaultMorphKeyType = null;
+    }
+
+    /** @inheritDoc */
+    protected function afterRefreshingDatabase()
+    {
+        Schema::create('integrations', function (Blueprint $table) {
+            $table->id();
+            $table->nullableMorphs('owner');
+            $table->string('provider');
+        });
+
+        $user = UserFactory::new()->create([
+            'name' => 'Taylor Otwell',
+            'email' => 'taylor@laravel.com',
+        ]);
+
+        DB::table('integrations')->insert([
+            'owner_type' => EloquentPolymorphicWithStringMorphTypeTestUser::class,
+            'owner_id' => $user->id,
+            'provider' => 'dummy_provider',
+        ]);
+    }
+
+    public function test_it_can_query_from_polymorphic_model()
+    {
+        $user = EloquentPolymorphicWithStringMorphTypeTestUser::first();
+
+        $user->loadMissing('integrations');
+
+        Assert::assertArraySubset([
+            ['owner_type' => EloquentPolymorphicWithStringMorphTypeTestUser::class, 'owner_id' => $user->getKey(), 'provider' => 'dummy_provider'],
+        ], EloquentPolymorphicWithStringMorphTypeTestIntegration::where('owner_id', $user->id)->where('owner_type', EloquentPolymorphicWithStringMorphTypeTestUser::class)->get()->toArray());
+    }
+
+    public function test_it_can_query_using_relationship()
+    {
+        $user = EloquentPolymorphicWithStringMorphTypeTestUser::first();
+
+        Assert::assertArraySubset([
+            ['owner_type' => EloquentPolymorphicWithStringMorphTypeTestUser::class, 'owner_id' => $user->getKey(), 'provider' => 'dummy_provider'],
+        ], $user->integrations()->get()->toArray());
+    }
+
+    public function test_it_can_query_using_load_missing()
+    {
+        $user = EloquentPolymorphicWithStringMorphTypeTestUser::query()->where('email', 'taylor@laravel.com')->first();
+
+        $user->loadMissing('integrations');
+
+        Assert::assertArraySubset([
+            'name' => 'Taylor Otwell',
+            'integrations' => [
+                ['owner_type' => EloquentPolymorphicWithStringMorphTypeTestUser::class, 'owner_id' => $user->getKey(), 'provider' => 'dummy_provider'],
+            ],
+        ], $user->toArray());
+    }
+}
+
+class EloquentPolymorphicWithStringMorphTypeTestUser extends Authenticatable
+{
+    protected $fillable = ['*'];
+    protected $table = 'users';
+
+    public function integrations()
+    {
+        return $this->morphMany(EloquentPolymorphicWithStringMorphTypeTestIntegration::class, 'owner');
+    }
+}
+
+class EloquentPolymorphicWithStringMorphTypeTestIntegration extends Model
+{
+    protected $fillable = ['*'];
+    protected $table = 'integrations';
+
+    public function owner()
+    {
+        return $this->morphTo('owner');
+    }
+}