The Traitor is a Caroline era stage play, a tragedy written by James Shirley. Along with The Cardinal, The Traitor is widely considered to represent the finest of Shirley's efforts in the genre, and to be among the best tragedies of its period. "It is impossible to find a more successful drama of its type than Shirley's Traitor."
The Traitor was licensed for performance by Sir Henry Herbert, the Master of the Revels, on 4 May 1631, and was acted by Queen Henrietta's Men at the Cockpit Theatre. The play was first published in 1635, with a dedication by Shirley to William Cavendish, 1st Duke of Newcastle.
In creating the character of Sciarrha, Shirley may have been influenced by Foreste in Sir William Davenant's The Cruel Brother (1627). Shirley's source for the play's subplot was the account of the murder of Buondelmonte in Le istoire fiorentine by Niccolò Machiavelli.
The play was revived during the Restoration era, in November 1660. King Charles II saw a public performance on 10 October 1661, a performance witnessed by Samuel Pepys. An adaptation of The Traitor was published in 1692, under its original title, but with the authorship credited to a "Mr. Rivers." In 1819, Richard Lalor Sheil produced an adaptation of The Traitor called Evadne.