St. Panteleimon, Byzantine church in Thessaloniki, Greece.

St. Panteleimon is a tetrastyle cross-in-square church with a narthex and two surviving chapels at its eastern end; the surrounding ambulatory has been destroyed. Its walls date to the late 13th or early 14th century, and the few original frescoes remain in the prothesis and diaconicon.

The building was constructed during the Byzantine period and was converted into a mosque named İshakiye Camii following the Ottoman conquest of the city in 1548. After 1912, the structure returned to Christian religious use and has functioned as a church since then.

The present name of Saint Panteleimon was given only after Ottoman rule ended in 1912; the original dedication is disputed. Scholars link the building to the Monastery of the Virgin Peribleptos, also called the Monastery of Kyr Isaac after Jacob, metropolitan bishop of Thessaloniki from 1295 to 1315, who took the monastic name Isaac. The monastery was a 14th-century intellectual centre where the scholars Thomas Magistros and Matthew Blastares taught and wrote.

The church is located at the intersection of Iasonidou and Arrianou streets in eastern Thessaloniki, close to the Tomb of Galerius. The site is easily accessible on foot and sits in a neighborhood containing other historical structures from different periods.

Inside the church, a marble fountain and the remains of a minaret base from the Ottoman period are still visible, documenting the building's long history of use. These remnants clearly show how the structure served different religious purposes over the centuries.