Greencastle or Green Castle may refer to:
Places
Germany
- Green Castle (Grünes Schloss), Weimar; see Duchess Anna Amalia Library
Ireland
- Greencastle, County Donegal, Republic of Ireland
- Greencastle, County Antrim, Northern Ireland, a townland and suburb of Belfast
- Greencastle, County Down, Northern Ireland
- Greencastle, County Tyrone, Northern Ireland
Scotland
- Green Castle, Portknockie, an Iron Age and Pictish promontory fort
United States
- Greencastle, Indiana, a city
- Greencastle, Missouri, a city
- Greencastle, Pennsylvania, a borough
- Greencastle, West Virginia, an unincorporated community
- Greencastle, Kanawha County, West Virginia, an unincorporated community
Other uses
- Greencastle (film)