Konstanz Minster or Konstanz Cathedral (German: Konstanzer Münster) is a historical building in Konstanz, southern Germany, the proto-cathedral of the former Roman Catholic diocese of Konstanz (dissolved in 1821).

The first mention of a church in Konstanz dedicated to the Virgin Mary was in 615. Documentary confirmation of the Episcopal church Ecclesia sanctae Mariae urbis Constantiae is dated to the mid 8th century. There is clear evidence indicating that it was located on the Cathedral Hill, where a late Romanesque fortification with an adjoining civilian settlement had been established. In 780, the church was mentioned in a confirmation of a contract by Charlemagne.

St Maurice’s Rotunda (Holy Sepulchre) was built in 940 on orders of Bishop Konrad (934 - 975) who was canonized in 1123.