Johanneskirche, Catholic church building in Favoriten, Austria

The Johanneskirche is a Roman Catholic church in Unterlaa, Favoriten, reached via Klederinger Straße. It is a single-nave building with a choir tower: the lower storey of the east tower serves as the secured chancel, roofed by a barrel vault with lunettes. A sacristy adjoins the tower to the south, and the Maltese cross appears on the tower tip and windows.

A Roman temple probably stood on this site before a small 9 × 7 m church was built over it, possibly by monks using stones from the Roman settlement; five burials found inside in 1974 may be those of its builders or of priests buried around 1030. In 1272 the church passed to the Knights of St John, who rebuilt the south side and added a hospice, destroyed with Unterlaa castle in 1465. It was largely destroyed during the 1683 siege and rebuilt with a nave in 1686; the sacristy followed in 1779.

The church's name comes from its 1272 transfer to the Knights Hospitaller, who dedicated it to their patron, John the Baptist. The Maltese cross, their emblem, appears on the tower tip and the windows. The order held sole manorial rights in Unterlaa from the late 13th century.

The church stands outside the old village core, reachable by public transport at the Johanneskapelle bus stop. The excavations around the church and the archaeological display room in a small side building, run by the Favoriten district museum, open from May to October on the first Sunday of each month.

The church stands on the site of a Roman cemetery; a tombstone found here names a Celtic man, Devomarus, and his family, evidence of settlement continuing after the first Roman village on the Johannesberg was destroyed. Excavations around the church have run since the 1960s.