diff --git a/src/calibre/ebooks/mobi/writer2/resources.py b/src/calibre/ebooks/mobi/writer2/resources.py
index 33b1a17d80..82c34828b7 100644
--- a/src/calibre/ebooks/mobi/writer2/resources.py
+++ b/src/calibre/ebooks/mobi/writer2/resources.py
@@ -88,6 +88,9 @@ class Resources(object):
         for item in self.oeb.manifest.values():
             if item.media_type not in OEB_RASTER_IMAGES:
                 continue
+            if item.media_type.lower() == 'image/webp':
+                self.log.info(f'Converting WebP image {item.href} to PNG')
+                item.convert_webp()
             try:
                 data = self.process_image(item.data)
             except:
diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index 957ded7bd1..e5298169bb 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -321,6 +321,7 @@ GIF_MIME       = types_map['.gif']
 JPEG_MIME      = types_map['.jpeg']
 PNG_MIME       = types_map['.png']
 SVG_MIME       = types_map['.svg']
+WEBP_MIME      = types_map['.webp']
 BINARY_MIME    = 'application/octet-stream'
 
 XHTML_CSS_NAMESPACE = '@namespace "%s";\n' % XHTML_NS
@@ -328,7 +329,7 @@ XHTML_CSS_NAMESPACE = '@namespace "%s";\n' % XHTML_NS
 OEB_STYLES        = {CSS_MIME, OEB_CSS_MIME, 'text/x-oeb-css', 'xhtml/css'}
 OEB_DOCS          = {XHTML_MIME, 'text/html', OEB_DOC_MIME,
                          'text/x-oeb-document'}
-OEB_RASTER_IMAGES = {GIF_MIME, JPEG_MIME, PNG_MIME}
+OEB_RASTER_IMAGES = {GIF_MIME, JPEG_MIME, PNG_MIME, WEBP_MIME}
 OEB_IMAGES        = {GIF_MIME, JPEG_MIME, PNG_MIME, SVG_MIME}
 
 MS_COVER_TYPE = 'other.ms-coverimage-standard'
@@ -1144,6 +1145,13 @@ class Manifest(object):
             href = os.path.normpath(href).replace('\\', '/')
             return href
 
+        def convert_webp(self):
+            from calibre.utils.img import image_and_format_from_data, image_to_data
+            img, fmt = image_and_format_from_data(self.data)
+            if fmt == 'webp' and not img.isNull():
+                self.data = image_to_data(img, fmt='PNG')
+                self.media_type = 'image/png'
+
     def __init__(self, oeb):
         self.oeb = oeb
         self.items = set()
diff --git a/src/calibre/test_build.py b/src/calibre/test_build.py
index f3a0e626ed..799bc02179 100644
--- a/src/calibre/test_build.py
+++ b/src/calibre/test_build.py
@@ -303,7 +303,7 @@ class BuildTest(unittest.TestCase):
         # hard-coded paths of the Qt installation should work. If they do not,
         # then it is a distro problem.
         fmts = set(map(lambda x: x.data().decode('utf-8'), QImageReader.supportedImageFormats()))  # no2to3
-        testf = {'jpg', 'png', 'svg', 'ico', 'gif'}
+        testf = {'jpg', 'png', 'svg', 'ico', 'gif', 'webp'}
         self.assertEqual(testf.intersection(fmts), testf, "Qt doesn't seem to be able to load some of its image plugins. Available plugins: %s" % fmts)
         data = P('images/blank.png', allow_user_override=False, data=True)
         img = image_from_data(data)