Plainfield is a town in Otsego County, New York, United States.

The Town of Plainfield is located in the northwestern corner of Otsego County.

According to the United States Census Bureau, the town has a total area of 29.5 square miles (76 km2), all land.

New York State Route 51 is a north–south highway in the eastern part of the town.

The racial makeup of the town was 98.48% White, 0.41% African American, 0.20% Asian, and 0.91% from two or more races.