Altmar is a village in Oswego County, New York, United States. The population was 351 at the 2000 census.
The Village of Altmar (formerly "Sand Bank") is in northern part of the Town of Albion at State Route 13 and County Route 22. Altmar is the seat of the town government.
The community was first settled in 1813 by Peter Henderson. The village was incorporated in 1876 as "Sand Bank." In 1890, the population was 551.