New York State Route 423 (NY 423) is an east–west state highway located within the town of Stillwater in Saratoga County, New York, in the United States. It extends for 3.86 miles (6.21 km) from an intersection with NY 9P on the eastern shore of Saratoga Lake in the hamlet of Snake Hill to a junction with NY 32 southwest of Saratoga National Historic Park. The road was acquired by the state of New York in the early 1920s and designated as NY 423 in the early 1930s.

Stillwater is a town in Saratoga County, New York, United States, with a population of 8,287 at the 2010 census. The town contains a village called Stillwater. The town is at the eastern border of the county, southeast of Saratoga Springs and borders both Rensselaer and Washington counties. Saratoga National Historical Park is located within the town's limits. There is a hamlet in Minerva, Essex County, New York, with the same name which has nothing to do with this town.