a town of the Prussian monarchy, East Prussia, in the government of Gumbinnen, on the left bank of the Niemen or Memel, which is here joined by the Tilse, 60 miles N.E. of Königsberg. It consists of one principal street, long, wide, and lined with well built houses; and it contains a castle, erected in 1537, a handsome Lutheran church, with a lofty spire, a Calvinistic church, a gymnasium, and several hospitals. Manufactures of woollen cloth, hosiery, leather, hardware, and arms are carried on here; and there is an important trade in corn, butter, timber, hemp, and flax. The river is navigable up to the town, and is crossed by a bridge of boats 1150 feet long. Tilsit is historically memorable for the peace concluded here in 1807 between Napoleon, the Emperor of Russia, and the King of Prussia. The three monarchs met on a raft moored in the river a little below the town. Pop. 13,748.