Leonardsville is a hamlet on the Unadilla River in the Town of Brookfield in Madison County, New York, United States.

[2] The community started as a number of small factories deriving power from a dam on the Unadilla River during the first decade of the 19th century.

As with many small communities, Leonardsville was given its name by the Post Office Department, which in this case named if after Reuben Leonard who, in his early years, ran a local grocery and dry goods business that became a convenient location to drop off mail for local residents.

Until the 1950s, when the manufacturing shops closed, Leonardsville was a stop on the Unadilla Valley Railway, had a milk station (now a recycling center) and a feed store.

None of the manufacturing buildings remain, but the former Crandall Department Store still stands and is now the regionally known Horned Dorset Restaurant.