Washington County is a county in the U.S. state of New York. As of the 2020 census, the population was 61,302. The county seat is Fort Edward. The county was named for U.S. President George Washington. The county is part of the Capital District region of the state.

When counties were established in the colony of New York in 1683, the present Washington County was part of Albany County. This was an enormous county, including the northern part of New York State as well as all of the present state of Vermont and, in theory, extending westward to the Pacific Ocean. This county was reduced in size on July 3, 1766, by the creation of Cumberland County, and further on March 16, 1770, by the creation of Gloucester County, both containing territory now in Vermont.

On March 12, 1772, what was left of Albany County was split into three parts, one remaining under the name Albany County. The other two were called Tryon County (later renamed Montgomery County) and Charlotte County.

On April 2, 1784, Charlotte County was renamed Washington County in honor of George Washington, the American Revolutionary War general and later President of the United States of America.

In 1788, Clinton County was split off from Washington County. This was a much larger area than the present Clinton County, including several other counties or county parts of the present New York State.

In 1791, the Town of Cambridge was transferred from Albany County to Washington County.

In 1813, Warren County was split off from Washington County.

In 1994, with the completion of the new municipal center, the county seat was moved from Hudson Falls to Fort Edward.