Tiedeman Island is an island in the Alexander Archipelago, east of Admiralty Island, about two-thirds up from the entrance of Seymour Canal, Southeast Alaska, United States. To its north is Swan Island. It was named by William Healy Dall of the U.S. Coast and Geodetic Survey, and published in the 1883 Coast Pilot. The first European to discover and chart the island was Joseph Whidbey, master of the HMS Discovery during George Vancouver's 1791-95 expedition, in 1794.