Isaac Dorislaus (1595 in Alkmaar, Holland – 10 May 1649 at The Hague, Holland) was an Anglo-Dutch lawyer and diplomat.
He was the son of a minister of the Dutch Reformed Church. He was educated at Leiden, removed to England about 1627, and was appointed to a lectureship in history at Cambridge,[1] where his attempt to justify the Dutch revolt against Spain led to his early resignation. In 1629 he was admitted a commoner of the College of Advocates. In 1632 he made his peace at court, and on two occasions acted as judge advocate, in the bishops war of 1640 and in 1642 in the army commanded by the Earl of Essex. In 1648 he became one of the judges of the admiralty court, and was sent on a diplomatic errand to the states general of Holland. He assisted in preparing the charge of high treason against Charles I, and, while negotiating an alliance between the Commonwealth and the Dutch Republic, was murdered at the Hague by royalist refugees. His remains were buried in Westminster Abbey, and moved in 1661 to St. Margaret's churchyard.