Chichagof Island is an island in the Alexander Archipelago of southeastern Alaska, 57°51' N 135°34' W. It is 5,398 km² (2,080 sq. miles) in area. It is 120 km (75 miles) long and 80 km (50 miles) wide.

Chichagof Island is north of Baranof Island. It is bounded by Chatham Strait to the east, Icy Strait to the northeast, Cross Sound to the northwest, the Gulf of Alaska to the west and Peril Strait to the south.

This island is named after Admiral Vasili Chichagov, a Russian Arctic explorer.