The Diomede Islands (/ˌdaɪ.əˈmiːdiː/; Russian:острова́ Диоми́да, ostrová Diomída), also known in Russia as Gvozdev Islands (Russian:острова́ Гво́здева, ostrová Gvozdjeva), consist of two rocky, mesa-like islands:

The Diomede Islands are located in the middle of the Bering Strait between mainland Alaska and Siberia, with the Chukchi Sea to the north and the Bering Sea to the south. 9.3 km (5.8 mi) to the southeast is Fairway Rock, which is generally not considered part of the Diomede Islands. Because they are separated by the International Date Line, Big Diomede is almost a day ahead of Little Diomede, but not completely; due to locally defined time zones, Big Diomede is only 21 hours ahead of Little Diomede (not 23 hours ahead - which is a common misconception). Because of this the islands are sometimes called Tomorrow Island (Big Diomede) and Yesterday Isle (Little Diomede).