Church of the Holy Trinity, Athens, Byzantine church on Filellinon Street, Athens, Greece.

The Church of the Holy Trinity is a Byzantine church located on Filellinon Street in central Athens with a commanding dome rising above an octagonal base. The building displays classical Byzantine design with a cross-in-square floor plan and incorporates decorative patterns on its exterior walls.

The present church was built before 1044, as graffiti naming the founder Stephen indicate, and was the katholikon of the Soteira Lykodimou convent. The convent was demolished in 1778 by Ottoman governor Hadji Ali Haseki; in 1821 a cannonball destroyed two-thirds of the dome and the west wall. Russia's Tsar Nicholas I acquired the ruin in 1847, and restoration under T. Vlasopoulos ran from 1850 to 1855.

The church is also called the Russian Church and St. Nikodemos, a modern corruption of Soteira Lykodimou, after the Lykodemos family linked to its founder Stephen. Its 19th-century frescoes are by Ludwig Thiersch, assisted by Nikiforos Lytras and Spyridon Hatzigiannopoulos; Thiersch gave Saint Paul the features of King Otto. It holds an icon of Saint Nicholas given by Queen Olga and icons brought by Russian refugees after 1917.

The church is centrally located in Athens and easy to reach if you want to explore the Orthodox heritage of the city. Keep in mind this is an active place of worship, so dress respectfully and avoid disturbing services.

The church is roughly three-quarters the size of the katholikon of Hosios Loukas, whose completed form of 1011 it closely copies in plan and decoration. A brick frieze of pseudo-Kufic motifs runs along three sides of the building, matching a similar band on the nearby Church of the Holy Apostles.