diff --git a/CHANGELOG.md b/CHANGELOG.md
index 69cf7f85..bce10232 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ All notable changes to `php-vips` will be documented in this file.
 - suppress autodoc of `composite` and `DemandStyle` [jcupitt]
 - update docs for 8.17 [jcupitt]
 - update docs for 8.18 [jcupitt]
+- add getGainmap [jcupitt]
 
 ## 2.5.0 - 2025-04-04
 
diff --git a/src/FFI.php b/src/FFI.php
index 8083adc6..722065d5 100644
--- a/src/FFI.php
+++ b/src/FFI.php
@@ -792,6 +792,12 @@ private static function init(): void
 CPP;
         }
 
+        if (self::atLeast(8, 18)) {
+            $vips_decls = $vips_decls . <<<'CPP'
+VipsImage* vips_image_get_gainmap(const VipsImage* image);
+CPP;
+        }
+
         Utils::debugLog("init", ["binding ..."]);
 
         /**
diff --git a/src/Image.php b/src/Image.php
index afc9b452..ecfa512d 100644
--- a/src/Image.php
+++ b/src/Image.php
@@ -1267,6 +1267,37 @@ public function getFields(): array
         return $fields;
     }
 
+    /**
+     * Get the gainmap attached to an image, or null for no gainmap.
+     *
+     * After modifying the gainmap, you'll need to use Image::set() to
+     * write it back to the image again under the name "gainmap", for example:
+     *
+     * ```php
+     * $gainmap = $image->getGainmap();
+     * if ($gainmap != null) {
+     *     $new_gainmap = $gainmap->crop(0, 0, 10, 10);
+     *     $image = $image->copy();
+     *     $image->set("gainmap", $new_gainmap);
+     * }
+     * ```
+     *
+     * @return ?Image
+     */
+    public function getGainmap(): ?Image
+    {
+        if (FFI::atLeast(8, 18)) {
+            $pointer = FFI::vips()->vips_image_get_gainmap($this->pointer);
+            if ($pointer == null) {
+                return null;
+            } else {
+                return new Image($pointer);
+            }
+        } else {
+            return null;
+        }
+    }
+
     /**
      * Set any property on the underlying image.
      *
diff --git a/tests/GainmapTest.php b/tests/GainmapTest.php
new file mode 100644
index 00000000..29fba6e5
--- /dev/null
+++ b/tests/GainmapTest.php
@@ -0,0 +1,61 @@
+<?php
+
+namespace Jcupitt\Vips\Test;
+
+use Generator;
+use Jcupitt\Vips;
+use PHPUnit\Framework\TestCase;
+
+class GainmapTest extends TestCase
+{
+    /**
+     * @var Vips\Image
+     */
+    private $image;
+
+    /**
+     * @var Vips\Image
+     */
+    private $no_gainmap_image;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        if (Vips\FFI::vips()->vips_type_find('VipsOperation', 'uhdrload') == 0) {
+            $this->markTestSkipped('requires libvips built with Ultra HDR support');
+        }
+
+        $filename = __DIR__ . '/images/ultra-hdr.jpg';
+        $this->image = Vips\Image::newFromFile($filename);
+
+        $filename = __DIR__ . '/images/img_0076.jpg';
+        $this->no_gainmap_image = Vips\Image::newFromFile($filename);
+    }
+
+    protected function tearDown(): void
+    {
+        unset($this->image);
+        unset($this->no_gainmap_image);
+    }
+
+    public function testVipsGetGainmap()
+    {
+        $gainmap = $this->image->getGainmap();
+        $this->assertEquals($gainmap->width, 960);
+
+        $gainmap = $this->no_gainmap_image->getGainmap();
+        $this->assertEquals($gainmap, null);
+    }
+
+    public function testVipsSetGainmap()
+    {
+        $gainmap = $this->image->getGainmap();
+        $new_gainmap = $gainmap->crop(0, 0, 10, 10);
+        $image = $this->image->copy();
+        $image->set("gainmap", $new_gainmap);
+
+        $gainmap = $image->getGainmap();
+        $this->assertEquals($gainmap->width, 10);
+    }
+}
diff --git a/tests/images/ultra-hdr.jpg b/tests/images/ultra-hdr.jpg
new file mode 100644
index 00000000..2e9a7ccb
Binary files /dev/null and b/tests/images/ultra-hdr.jpg differ