Antrim Castle or Massereene Castle was a castle in Antrim, County Antrim, Northern Ireland, on the banks of the Sixmilewater River. It was erected in stages between 1613 and 1662. It was destroyed by fire in 1922 and finally demolished in the 1970s. The only evidence of the castle is a slightly raised grassed platform as well as a freestanding Italianate tower which was built in 1887 and a gatehouse.