Duncan Passage is a strait in the Bay of Bengal.

It is about 48 km (30 mi) wide; it separates Rutland Island (part of Great Andaman and South Andaman administrative division) to the north, and Little Andaman to the south.

West of Duncan Passage is the Bay of Bengal; east is the Andaman Sea.

It lies within the exclusive economic zone of India protected by the integrated tri-services Andaman and Nicobar Command of Indian Military.

Several small islands and islets lie along the passage.