The Apostolic Vicariate of Thessaloniki (Latin: Vicariatus Apostolicus Thessalonicensis) is a Latin Church ecclesiastical territory or apostolic vicariate of the Catholic Church in northern continental Greece.

It is exempt to the Holy See and is not part of any ecclesiastical province, and remains vacant under apostolic administrators since its only proper apostolic vicar, Alessandro Guidati, was promoted Archbishop of Naxos, Andros, Tinos and Mykonos in 1929.

[1] The vicariate was established in 1926 as Apostolic Vicariate of Thessalonica, by Pope Pius XI in the apostolic brief "In sublimi Principis",[2] from canonical territory split off from the Roman Catholic Apostolic Vicariate of Constantinople, comprising the Greek prefectures of Thessaloniki, Kavala, Xanthi, Volos, Larisa and Giannitsa.

Since then, the Vicariate covers the entire territory of northern Greece, including regions of Greek Macedonia, Greek Thrace and Thessaly.

In 2014, it served 7,376 Catholics (0.2% of the local population) on 57,550 km2 in 4 parishes and 4 missions with 10 priests (3 diocesan, 7 religious) and 16 lay religious (9 brothers, 7 sisters).