Ambrosius Eßer OP (born Klaus Eßer, also spelled Eszer, or Esser; 19 November 1933 in Düsseldorf – 12 April 2010 in Berlin) was a German church historian and member of the Dominican Order. He died of a pulmonary embolism.
Eszer served for many years as professor at the Pontifical University of St. Thomas Aquinas, Angelicum in Rome, Italy.