Umm an Nasan island (Arabic: ام النعسان) is the fourth largest island in Bahrain, after Bahrain Island, Hawar Island and Muharraq Island. It is privately owned by King Hamad bin Isa Al Khalifa, and is off limits to ordinary citizens. It is connected to Bahrain Island through the King Fahd Causeway. There is little development on the island other than two palaces for the King and some gardens. There is also a small population of black buck introduced to the island.
Umm an Nasan lies in the Gulf of Bahrain in Persian Gulf to the west of Bahrain Island, and to the east of the Saudi coastal city of Khobar.
Coordinates: 26°8′41.17″N 50°24′7.49″E / 26.1447694°N 50.4020806°E / 26.1447694; 50.4020806