Otto Julius Bierbaum (28 June 1865 – 1 February 1910) was a German writer.
As a poet he used forms like the Minnesang or the folksong and the Anacreontics style.
In 1897 Bierbaum published his novel Stilpe which inspired Ernst von Wolzogen to establish, in 1901, the first cabaret venue ever in Berlin, the Überbrettl .
His novel Zäpfel Kerns Abenteuer was an adaptation of Carlo Collodi's Pinocchio.
Bierbaum's final novel, Yankeedoodlefahrt, was published in 1909 and is the source of the adage "Humor ist, wenn man trotzdem lacht" ("Humor is when you laugh anyway"), which has become a proverb in modern German.