or Rathenau, a town of Prussia, in the province of Brandenburg and circle of Potsdam, on the Havel, 48 miles W. of Berlin. It contains a church with a newly-erected Gothic tower, a gymnasium, and a girls' school. There is also a monument and a statue of the elector Frederick-William. Among the manufactures, the most important is that of optical instruments; fishing, brewing, distilling, and navigation, give employment to many of the people. A victory was gained here in 1675 by the troops of Brandenburg over the Swedes. Pop. 6432.