The Gallus chapel (German: Gallus-Kapelle) is a listed heritage building in the municipality of Greifensee, Canton of Zürich, Switzerland.
Nobleman Hermann IV (the younger Marshal) of Landenberg donated, for his salvation and on his wife favour, this chapel around 1330-1340. The triangular building is considered to be the oldest intact Gothic monument of the medieval town. Originally, it was integrated into the eastern corner of the city walls as a Wehrkirche (fortified church), repeating in its ground floor the plan of the small town. In the castle of Greifensee, there is a small chapel dedicated to St Catherine which was built at the same time, given by Hermann IV, too. For centuries, this tiny chapel has been the Parish church of the city of Greifensee.