Mariä Himmelfahrt, Catholic parish church in Aichach, Germany.

Mariä Himmelfahrt is the Catholic parish church of Aichach, first documented in 1153 and rebuilt around 1450 into its present form, when all three naves were raised and six windows in the central nave's upper walls were walled up. Two small chapels were added to the south aisle in 1709 and 1777. The interior was repainted violet and fitted with electric lights in 1906–08 under architect Richard Berndl.

A church at Aichach was first recorded on 17 September 1153 and was handed to the Teutonic Order by Duke Ludwig the Kelheimer in 1210. Around 1450 the Romanesque nave was rebuilt in its present form, with all three aisles raised and six windows in the clerestory walled up. Two small chapels were added to the south aisle in 1709 and 1777, and the interior was baroquised in 1771.

The high altar is a simplified copy of the one Egid Quirin Asam made for Osterhofen, built by the church carpenter Johann Anton Wiest of Schrobenhausen. The Anna Selbdritt window dates from the early 16th century, and the sandstone Stations of the Cross were carved around 1908 by sculptor Georg Busch.

The 1989 Klais organ has 42 stops and 2,773 pipes, 2,531 of tin and 242 of wood, set in a reused 1908 Art Nouveau case; it was fully overhauled in 2020. The church is an active parish, so visiting is easiest outside service times. Since March 2020 bells 3–6 have been silent for structural reasons, leaving the two smallest bells ringing.

The church houses Art Nouveau Stations of the Cross designed by Georg Busch that underwent major restoration work in 2017. This artistic series represents a less visible layer of the building's heritage that visitors often overlook when first entering.