Anckarstroem, Or Ankarstrom, Johan Jakob, the assassin of Gustavus III. of Sweden, born about 1760, executed at Stockholm, April 29, 1792. The son of a superior officer, he became a page at the court of Gustavus, and subsequently ensign in the royal body guard; but in 1783 he withdrew from military service, and settled into country life. As a partisan of the old aristocratic party he vehemently opposed the measures of the king, who followed up his work, begun on his accession, of restrict-ing the power of the senate and the nobility. He became implicated in the seditious movements of the island of Gothland, and was tried for treason in 1790, but acquitted for want of evidence. The same year he engaged in a conspiracy with General Pechlin, Count Horn, Count Ribbing, Baron Bjelke, Colonel Liljehorn, and other discontented nobles, to kill the king; and on casting lots who should execute the deed, the choice fell upon Anckarstroom. On the night of March 15, 1792, at a masked ball, he shot the king, inflicting a fatal wound. Anckarstroem was at once arrested, tried, convicted, and sentenced, first to be ignominiously flogged, and then to die on the scaffold.

He met his fate with great firmness, exulting to the last in the righteousness of his course, and refusing to disclose the names of his accomplices.