Samosir Regency is an inland regency in North Sumatra. It was created on 18 December 2003 by splitting away the western districts of the former Toba Samosir Regency. The regency covers a land area of 1,444.25 square kilometres, including the whole of Samosir Island in the inland sea of Lake Toba. It had a population of 119,653 at the 2010 census and 136,441 at the 2020 Census; the official estimate for mid 2025 was 144,813. Its administrative seat is the town of Pangururan on the west coast of Samosir Island.