St. Mary's Cathedral (Estonian: Toomkirik, German: Ritter- und Domkirche, full name: The Episcopal Cathedral of the Holy Virgin Mary, Tallinn, Estonian: Tallinna Püha Neitsi Maarja Piiskoplik Toomkirik) is a Lutheran cathedral church located on the Toompea hill in the medieval central part of Tallinn, the capital city of Estonia.

Established in the 13th century, it is the oldest church in Tallinn and mainland Estonia, and the only building in Toompea which survived the 17th-century fire.

The monks were killed in a conflict between the Knights of the Sword and vassals supporting the pope's legate in 1233, and the church was thus desecrated.

The church suffered considerable damage in the great fire of 1684 when the entire wooden furnishings were destroyed.

The new pulpit with figures of the apostles (1686) and the altarpiece (1696) were made by the Estonian sculptor and carver Christian Ackermann.

Among the people buried in the cathedral are the Bohemian nobleman Jindřich Matyáš Thurn, one of leaders of the Protestant revolt against Emperor Ferdinand II and in events that led to the Thirty Years' War; the Swedish general Pontus De la Gardie and his wife, Sofia Johansdotter Gyllenhielm (King John III's daughter); as well as the Scotsman Samuel Greig (formerly Samuil Karlovich Greig of the Russian Navy); the Swedish field marshals and cousins Otto Wilhelm and Fabian von Fersen; and the Russian navigator, Adam Johann von Krusenstern.