Paul Louis François Spaak (5 July 1871 – 8 May 1936) was a Belgian lawyer, poet, literary historian, and playwright.

Born in Ixelles, Spaak graduated in law at the Université Libre de Bruxelles in 1894. On 22 July 1894, he married Marie Janson, daughter of Paul Janson. The couple had four children, of whom Paul-Henri Spaak, later Belgian Prime Minister like his uncle Paul-Emile Janson, was the most famous. Paul Spaak was a member of Royal Academy of Belgium from 19 August 1920 until 8 May 1936.

From 1920, up until his death, Paul Spaak was co-director of the Théâtre Royal de la Monnaie. He shared this position with Maurice Corneil de Thoran and Jean Van Glabbeke.