Joseph Ewart FRSE (30 April 1759 – 27 January 1792) was a Scottish diplomat, mainly based in Berlin in Prussia (now Germany) .
He was educated at Dumfries Parish School then went to the University of Edinburgh, and then acted as travelling tutor to Macdonald of Clan Ronald.
Pitt's design, assisted by Lord Malmesbury, was to induce Frederick William of Prussia to intervene in the affairs of Holland; to put down the revolutionary party there; and to re-establish the Prince of Orange as a stadt-holder.
Of his subsequent conduct at the court of Berlin there are contradictory reports, for the French revolution commenced in 1789, and partisans and opponents of the English foreign policy of that period represent the minister's behaviour in different lights.
A statement that he died out of his mind, and another (by Wraxell) that his death was due to foul play of the Empress Catherine, are entirely disproved by facts preserved in the family papers.