In Good King Charles's Golden Days is a play by George Bernard Shaw, subtitled A True History that Never Happened.

A discussion play, the issues of nature, science, power and leadership are debated between Charles ("Mr Rowley"), Isaac Newton, George Fox, and the artist Godfrey Kneller, with interventions by three of the king's mistresses (Barbara Villiers, Louise de Kérouaille, and Nell Gwynn).

Billed as "A history lesson in three scenes by Bernard Shaw", the first production was at the Malvern Festival Theatre on 12 August 1939, directed by H. K. Ayliff and designed by Paul Shelving.

[2] The first North American production was on 24 January 1957 at the Downtown Theater on New York's East 4th Street, where it ran for nearly two years, one of the longest runs of any Shaw play in the USA (as noted by Lawrence Langner).

A BBC production in the Play of the Month series, starring Sir John Gielgud as King Charles, was broadcast in February 1970.