Sullivan County is a county located in the U.S. state of New York. As of 2000, the population was 73,966. The county seat is Monticello. The name is in honor of Major General John Sullivan, who was a hero in the American Revolutionary War.

As of the census˛ of 2000, there were 73,966 people, 27,661 households, and 18,311 families residing in the county. The population density was 29/km˛ (76/mi˛). There were 44,730 housing units at an average density of 18/km˛ (46/mi˛). The racial makeup of the county was 85.31% White, 8.51% Black or African American, 0.27% Native American, 1.12% Asian, 0.04% Pacific Islander, 2.89% from other races, and 1.87% from two or more races. 9.25% of the population were Hispanic or Latino of any race.