The Church of Saint Demetrius (Serbian: Црква светог Димитрија), locally known as the New Orthodox Church or the Great Church, is a Serbian Orthodox church located in the city Sremska Mitrovica, in the autonomous province of Vojvodina, Serbia. The building is the largest Orthodox place of worship in Sremska Mitrovica and among the largest ones in the historical region of Syrmia. It belongs to the Eparchy of Srem of the Serbian Orthodox Church. The church is dedicated to the city's patron saint, St. Demetrius of Sirmium, after whom the city is named. It has been declared an Immovable Cultural Monument of Great Importance.

The church is designed with a single-nave layout, featuring a spacious semicircular apse at the east end and a tall bell tower rising above the western façade. Over the years the building has undergone numerous interventions, the first of which took place in 1811. The church was originally dedicated to St. Stephen yet it was later rededicated to St. Demetrius in 1997. The relics of St. Demetrius were discovered in the city centre in the summer of 1978. St. Demetrius was a deacon of Bishop Irenaeus, and both were executed by Roman legionaries on one of the bridges over the Sava River in imperial Sirmium in 204 AD.

• Eparchy of Srem