Münsterplatz, Cultural heritage square in Mainz-Altstadt, Germany.

Münsterplatz is the square where Große Bleiche, Schillerstraße, Bilhildisstraße, Binger Straße and Bahnhofstraße meet in Mainz's old town. Its dominant building is the telegraph office, built 1928–1930 to designs by Gottlob Schaupp, which exceeds every other building on the square in width and height. Opposite stands the tax office, begun in 1929 and finished in 1931; the two offices echo each other in symmetry, window arrangement and building volume, while the nearby Baroque Erthaler Hof contrasts with their unornamented New Objectivity facades.

The square takes its name from the Münstertor gate and Altmünster Abbey, both once on this site; the gate was demolished in 1877 during the city's expansion, but the name stayed. Binger Straße and Mittlere Bleiche were later extended to the square, making it a traffic hub, and Altmünster houses were torn down as it grew. In 1926 a competition won by H. F. W. Kramer and Gottlob Schaupp led to the Telegraph Office (1928–1930) and the Tax Office (1929–1931).

The name comes from the Münstertor gate of the Mainz fortress and the former Altmünster Abbey, and it survived the gate's demolition in 1877. The square is a traffic junction where Große Bleiche, Schillerstraße, Bilhildisstraße, Binger Straße and Bahnhofstraße meet, and since 2018 it has been a redesigned open space in front of the telegraph office.

The square is easily accessible on foot and well-connected by public transportation, with multiple bus stops nearby. Parking is available in the surrounding streets, and the flat surface makes it accessible for all visitors.

The 1926 competition for the plots of the demolished Altmünster houses was won by Frankfurt architects H. F. W. Kramer and Gottlob Schaupp, who designed the Telegraph Office (built 1928–1930) and the Tax Office (1929–1931). The Telegraph Office is the tallest and widest building on the square, and its massing answers the Tax Office while contrasting with the ornate Baroque Erthaler Hof nearby.