Martinsburg is a town in Lewis County, New York, United States. The population was 1,433 at the 2010 census. The town is named after its founding father, General Walter Martin.

Lewis County is a county located in the U.S. state of New York. As of the 2020 census, the population was 26,582, making it the fourth-least populous county in New York. Its county seat is Lowville. The county is named after Morgan Lewis, the Governor of New York when the county was established. The county is part of the North Country region of the state.