The Old Synagogue (German: Alte Synagoge; Yiddish: אלטע שול, ערפורט; Hebrew: בית הכנסת הישן (ארפורט)) is a former Jewish congregation and synagogue, located in Erfurt, Thuringia, Germany.

Dating from the late 11th century, the synagogue is one of the best preserved Medieval synagogues in Europe. Most parts of the building date from around 1250–1320. Due to the fact that its roof is intact, it is thought to be the oldest synagogue building intact in Europe and the world.

Since 2009 it has been used as a museum of local Jewish history. It houses the Erfurt Treasure, a hoard of medieval coins, goldsmiths' work and jewellery found in 1998. It also has facsimiles of the Erfurt Hebrew Manuscripts, an important collection of 12th–14th century religious texts that belonged to the medieval Jewish community of Erfurt.

The Historic Synagogues of Europe project, carried out by the Center for Jewish Art at the Hebrew University of Jerusalem, has given the Old Synagogue, Erfurt its highest level of significance rating: 4 (International) – "The building is of outstanding architectural, urban or historical importance. It has unique features and/or is especially influential internationally as an architectural pattern."

In 2023, the Old Synagogue, Mikveh, and the 'Stone House', a secular building from c. 1250 in Erfurt's medieval city centre which had Jewish owners, were inscribed on the UNESCO World Heritage List in 2023 because of their exceptional preservation and testimony to the life of medieval Jewish communities.