John Julius Angerstein (1735 – 22 January 1823)[1] was a London businessman and Lloyd's underwriter, a patron of the fine arts and a collector.

Joseph Payne and widow of Thomas Lucas, a director of the South Sea Company, president of Guy's Hospital and West Indies merchant).

A portrait of Angerstein and his second wife, Eliza, by Thomas Lawrence was exhibited at the Royal Academy in 1792 (now held by The Louvre museum, Paris).

[5] Angerstein was chairman of Lloyd's from 1790 to 1796 and counted King George III, British Prime Minister William Pitt the Younger and artist Sir Thomas Lawrence[note 2] among his friends.

After a number of knife attacks on women by the so-called "London Monster", Angerstein promised a reward of £100 for capture of the perpetrator.

Following the death of William Pitt the Younger in 1806, he commissioned Thomas Lawrence to paint a portrait of the former Prime Minister which is now in the Waterloo Chamber of Windsor Castle.