Hans Henny Jahnn (17 December 1894, Stellingen – 29 November 1959, Hamburg) was a German playwright, novelist, and organ-builder.
As a playwright, he wrote: Pastor Ephraim Magnus (1917), which The Cambridge Guide to Theatre describes as a nihilistic, Expressionist play "stuffed with perversities and sado-masochistic motifs"; Coronation of Richard III (1922; "equally lurid"); and a version of Medea (1926).
Later works include the novel Perrudja, an unfinished trilogy of novels River without Banks (Fluss ohne Ufer), the drama Thomas Chatterton (1955; staged by Gustaf Gründgens in 1956), and the novella The Night of Lead.
Erwin Piscator staged Jahnn's The Dusty Rainbow (Der staubige Regenbogen) in 1961.Jahnn was also a music publisher, focusing on 17th-century organ music.
He was a contemporary of organ-builder Rudolf von Beckerath.