The Mousetrap

Long-running play by Agatha Christie. 

World premiere: Theatre Royal Nottingham, 6 October 1952 (directed by Peter Cotes)

London run: 25 November 1952 at the Ambassadors Theatre (to Saturday 23 March 1974)
The show then moved next-door to the larger St Martins Theatre, where the run continued 2 days later, from Monday 25 March 1974, where it is still running today, making it by far the longest-running theatrical event anywhere in the world.

A long run at the Toronto Truck Theatre, Toronto, Ontario, Canada opened on 19 August 1977 and closed on 18 January 2004 (26 years and over 9000 performances).