Kiritimati Kiritimati or Christmas Island is a Pacific Ocean atoll in the northern Line Islands and part of the Republic of Kiribati.The island has the greatest land area of any coral atoll in the worldlagoon is about the same size. The atoll is about in perimeter, while the lagoon shoreline extends for over . Kiritimati comprises over 70% of the total land area of Kiribati, a nation encompassing 33 Pacific atolls and islands.