Gun Island is one of the larger islands in the Pelsaert Group of the Houtman Abrolhos, in the Indian Ocean off the west coast of Australia. It is nominally at 28°53′10″S 113°51′35″E / 28.88611°S 113.85972°E,[1] about 4 km (2.5 mi) north and east of Half Moon Reef and is a flat limestone outcrop of about 800 by 420 metres (2,620 by 1,380 ft) in size. The island is part of the Houtman Abrolhos Important Bird Area, identified as such by BirdLife International because of its importance for supporting large numbers of breeding seabirds.[2]