St. Johns Co-Cathedral (Maltese: Kon-Katidral ta’ San Ġwann), located in Valletta, Malta, was built by the Knights of Malta between 1573 and 1578, having been commissioned in 1572 by Grand Master Jean de la Cassière as the conventual church of the Order of the Knights Hospitaller of St John, known as the Knights of Malta. The Church was designed by the Maltese military architect Glormu Cassar who designed several of the more prominent buildings in Valletta.