Archangel Island, Nature reserve in Gulf of California, Mexico.

Archangel Island is an uninhabited island and national park reserve in the Gulf of California, 931 square kilometres in area and the second largest of the Midriff Islands. A mountain chain runs its full 69 km length, reaching 1,305 m, and the west coast is largely inaccessible where mountains stand at the shore. Flat alluvial fans at the mouths of dry washes, mostly on the east coast, are the few landing places.

The island never developed permanent human settlements throughout its history, with only occasional visits from hunting groups. These visits were seasonal and focused on obtaining food and resources.

The island's Seri names mark its two halves: Xazl Iimt, "where pumas live", in the north and Tjamojíil Yacáai in the south. Its Spanish name, Guardian Angel Island, comes from the Jesuit missionary Wenceslao Link, who recorded his observations here in 1760 before founding the San Francisco Borja de Ádac mission 37 km from the coast.

The island lies 33 km northeast of Bahía de los Ángeles, across the Canal de Ballenas, which narrows to 13 km. Mountains at or near the shore make much of the west coast inaccessible; the flat alluvial fans at the mouths of washes, mostly on the east coast, are the practical landing places. There is no fresh water beyond rain-fed washes, so bring all drinking water.

The channel between this place and the mainland serves as a year-round feeding ground for fin whales. Visitors may encounter these large marine mammals in their natural habitat.