The Church of St. Nicholas (German: St.-Nikolai-Kirche) is a Gothic Revival cathedral that was formerly one of the five Lutheran Hauptkirchen (main churches) in the city of Hamburg, Germany. The original chapel, a wooden building, was completed in 1195. It was replaced by a brick church in the 14th century, which was eventually destroyed by fire in 1842. The church was completely rebuilt by 1874, and was the tallest building in the world from 1874 to 1876. It was designed by the English architect George Gilbert Scott.

The bombing of Hamburg in World War II destroyed the bulk of the church. The removal of the rubble left only its crypt, its site and tall-spired tower, largely hollow save for a large set of bells. These ruins continue to serve as a memorial and an important architectural landmark. When Hamburg residents mention the Nikolaikirche, it is generally to this church that they are referring, and not the new Hauptkirche dedicated to Saint Nicholas in the Harvestehude district. The remains of the old church are the second-tallest structure in Hamburg. In 2005, an elevator was installed to a 75.3-metre-high (247 ft) platform.