Coordinates: 9°56′13.13″S 150°12′41.40″W / 9.9369806°S 150.2115°W / -9.9369806; -150.2115

Caroline Island or Caroline Atoll (also known as Millennium Island and Beccisa Island), is the easternmost of the uninhabited coral atolls which comprise the southern Line Islands in the central Pacific Ocean.

First sighted by Europeans in 1606, claimed by the United Kingdom in 1868, and part of the Republic of Kiribati since the island nation's independence in 1979, Caroline Island has remained relatively untouched and is considered one of the world's most pristine tropical islands, despite guano mining, copra harvesting, and human habitation in the 19th and 20th centuries. It is home to one of the world's largest populations of the coconut crab and is an important breeding site for seabirds, most notably the sooty tern.

The atoll is best known for its role in celebrations surrounding the arrival of the year 2000— a 1995 realignment of the International Date Line made Caroline Island one of the first points of land on Earth to reach January 1, 2000 on the calendar.