Easter Greenock Castle was a castle of unknown design near the burgh of Greenock, Scotland. Built sometime in the mid-sixteenth century, the castle formed the centre of the lands and estates of Cartsburn and Easter Greenock. These belonged to the Crawfords of Kilbirnie in Ayrshire who acquired them during the reign of Mary, Queen of Scots. Cartsburn extends from the Carts Burn on the west along the River Clyde to the point where the boundary falls out at Old Clyde Forge. The lands of Cartsburn were originally part of the barony of Kilbirnie and became the patrimony of a younger brother of that family, whose posterity ended in the person of David Crawford of Cartsburn in the reign of Charles I.