St. Catherine's Church (German: St. Katharinen) is one of the five principal Lutheran churches (Hauptkirchen) of Hamburg, Germany. The base of its spire, dating from the 13th century, is the second oldest building preserved in the city, after the lighthouse on Neuwerk island. It is situated on an island near what was formerly the southern boundary of the medieval city, opposite the historic harbour area on the Elbe river. It traditionally served as the church of the seamen.