Knox Atoll (Marshallese: Ņadikdik, [ɳˠɑɑ̯r̪ʲi͡ɯɡ(ɯ͡i)r̪ʲi͡ɯk]) is an uninhabited coral atoll of 18 islands in the Pacific Ocean, and is the southernmost atoll of the Ratak Chain of the Marshall Islands. The total land area is only 0.98 square kilometres (0.38 sq mi), but it encloses a largely sand-filled lagoon with an area of 3.42 square kilometres (1.32 sq mi). The atoll measures 11 kilometres (6.8 mi) in length and is 2 kilometres (1.2 mi) wide. The largest islets, located on the western and northern sides, include Aelingeo, Nadikdik and Nariktal.