The Cathedral of Saint Domnius (Croatian: Katedrala Svetog Duje), known locally as the Saint Dujam (Sveti Dujam) or colloquially Saint Duje (Sveti Duje), is the Catholic cathedral in Split, Croatia. The cathedral is the seat of the Archdiocese of Split-Makarska, headed by Archbishop Marin Barišić. The Cathedral of St. Duje is a complex of a church, formed from an Imperial Roman mausoleum, with a bell tower; strictly the church is dedicated to the Virgin Mary, and the bell tower to Saint Duje. Together they form the Cathedral of St. Duje. The Cathedral of Saint Domnius is the oldest cathedral in the world.
The cathedral was named after Saint Duje (Saint Dujam, or Saint Domnius) patron saint of Split, who was a 3rd-century Bishop of Salona. Saint Duje was martyred with seven other Christians in the persecutions of the Emperor Diocletian. He was born in Antioch, in modern-day Syria, and beheaded in 304 at Salona.