Banten Bay, also known as Bantam Bay, is a bay in Banten province, near the northwest tip of Java, Indonesia. It is part of the Java Sea and has a total water surface of approximately 150 square kilometres (58 sq mi; 44 sq nmi) and an average depth of 7 metres (23 ft). It includes marine ecosystems such as seagrass fields and coral reefs, and a major international bird sanctuary.^[1] The coastal zone, including the nearby cities of Serang and the port of Merak, is undergoing rapid industrialisation.

The bay has been the site of two major naval battles:

• Battle of Bantam, 1601, during the Dutch-Portuguese War
• Battle of Sunda Strait, 1942, during World War II