The King's House was a building in Osgiliath where the Kings of Gondor and their families lived during the first part of the Third Age. After the abandonment of Osgiliath and the removal of the Kings to Minas Tirith in T.A. 1640, the original King's House was presumably no longer used.
Queen Berúthiel was said to prefer the King's House to her husband's residence by the Sea near Pelargir. While living there, she kept the inside bare and filled the courtyard with strange and frightening sculptures.