The Church of St Nicholas (Bulgarian: църква „Свети Никола“, tsarkva „Sveti Nikola“) is a partially preserved medieval Eastern Orthodox church in the town of Melnik in Blagoevgrad Province, southwestern Bulgaria. Dating to the late 12th century, it stands on top of an ancient Thracian sanctuary and a 5th-century basilica. In the Middle Ages, the church served as the cathedral of Melnik's bishop. The interior of the church features frescoes of rarely depicted scenes, as well as a 13th-century inscription. Its bell tower used to house one of the oldest extant church bells in Europe, discovered by archaeologists in the 2000s.
The Church of St Nicholas lies on top of the eponymous hill of Sveti Nikola ("Saint Nicholas") just south of the town of Melnik. The church occupies a location which hosted other sacred buildings in Antiquity. A Thracian sanctuary devoted to the goddess Bendis, the Thracian variant of Artemis, stood at the place before a Christian basilica was built in the 5th century. However, the older church did not survive for long, as it was ruined by the end of the 6th century.
The Church of St Nicholas is generally dated to the late 12th century, a time when Melnik was ruled by both Byzantium and the Second Bulgarian Empire. There is a single opinion which links the building of the church with the rule of Prince Boris I of Bulgaria (r. 852–889) and the period shortly after the Christianization of Bulgaria, though the evidence for this is not accepted by most scholars. A second stage of construction followed in the first half of the 13th century, when the Church of St Nicholas was elevated to the seat of a bishop. In order for the church to better fulfil that purpose, a fence and additional buildings were constructed around it to form a compound.