The Gulf of Bahrain is a bay on the west side of the Persian Gulf situated on the East Coast of Saudi Arabia, disconnected from the main body of water by the Qatar peninsula, that surrounds the six islands and small islets of Bahrain. The Hawar Islands that belong to Bahrain, are also located in the Gulf, to the south-east of Bahrain, off the coast of Qatar. Saudi Arabia is connected to Bahrain via the King Fahd Causeway that crosses the western section of the Gulf.

The King Fahd Causeway is comprised of five bridges that are linked by otherwise solid embankments and they were designed to minimise any environmental impact. The waters of the Gulf are generally shallow and have a small thermal capacity with wide fluctuations in temperature that range from 14 to 35 °C around the coasts. The water is also around 10% more saline than in other parts of the Persian Gulf.

The Gulf of Bahrain contains various areas that are important to the biodiversity of the area including coral reefs, mangrove thickets, mudflats and seagrass meadows, that provide habitats for juvenile fish, turtles, invertebrates and Dugongs. The Hawar Islands provide a nesting ground for many bird species including Socotra cormorants.

Unfortunately, the coral reefs have been damaged and destroyed in places due to land expansion projects by Bahrain, which involve dredging the seabed and depositing material around its coast.