Bintuni Bay (Indonesian: Teluk Bintuni) is the eastward extension or inner bay of Berau Gulf in western New Guinea. It separates the Bird's Head Peninsula on the north from the Bomberai Peninsula on the south. Administratively it is part of West Papua, Indonesia. The bay is 12 miles (19.3 km) wide at its entrance and there are extensive marshes along the shore.

Bintuni Bay contains the largest continuous area of mangroves in Indonesia, and is second only to the Sundarbans of India and Bangladesh. Over 30 species of mangroves have been recorded in the bay, and undisturbed mangrove stands can grow up to 30 metres tall.

Bintuni Bay Nature Reserve, also known as Teluk Bintuni Nature Reserve, protects the mangrove wetlands in the northeastern portion of the bay. It has an area of 1248.51 km.