Old Greencastle Historic District is a national historic district in Greencastle, Putnam County, Indiana. The district encompasses 79 contributing buildings in a predominantly residential section of Greencastle. The district developed between about 1826 and 1961 and includes notable examples of Federal, Greek Revival, Italianate, Stick Style, Prairie School, and Bungalow / American Craftsman-style architecture. Notable buildings include the Davidson House (c. 1826) and Gillespie-Lynch House (1830).
It was added to the National Register of Historic Places in 2011.