Richard Langhorne (c. 1624 – 14 July 1679) was an English barrister and Catholic martyr, who was executed on a false charge of treason as part of the fabricated Popish Plot.

[1] When Oates and Israel Tonge unleashed their entirely fictitious Popish Plot, a non-existent Catholic conspiracy to kill King Charles II, in September 1678, three Jesuits and a Benedictine were arrested.

Oates claimed, and was corroborated by the notorious informer and confidence trickster William Bedloe, that Langhorne's earlier correspondence dealt with the conspiracy to kill the King.

His main defence consisted of an attack on the character of the Crown's principal witnesses, Oates and Bedloe, but since the judges were well aware of the deplorable past lives of both men, this seems to have made little impression.

[4] He also called a number of students from St Omer to prove that Oates had been at the college on the crucial dates when he claimed to be in London, but the public mood was so hostile to Catholics that the witnesses were barely able to make themselves heard over the roar of the crowd, and some of them were assaulted as they left the Court.

[5] Ironically, some of the same witnesses appeared for the prosecution at Oates' own trial for perjury in 1685, where the crowd treated them courteously, and the jury was told to weigh their evidence with the greatest seriousness.