Witsen wrote under a pseudonym in the literary magazine De Nieuwe Gids, which he also supported financially.His circle of friends included the painters George Hendrik Breitner, Isaac Israëls, and Jan Veth and the writers Lodewijk van Deyssel, Albert Verwey, Willem Kloos, and Herman Gorter.
Willem de Kooning | Willem Dafoe | Willem Blaeu | Willem Janszoon | Willem Mengelberg | Willem Roggeman | Herman Willem Daendels | Willem Drees | Willem-Alexander of the Netherlands | Willem van Otterloo | Willem Schouten | Willem Kloos | Willem Klein | Willem II (football club) | Willem II | Willem de Vlamingh | Willem Buiter | John Willem Gran | Willem Verstegen | Willem van Hoogstraten | Willem van Enckevoirt | Willem van de Sande Bakhuyzen | Willem Sassen | Willem P.C. Stemmer | Willem Frederik Hermans | Willem C. Vis Moot | Willem B. Drees | Willem Abraham Wythoff | Pieter Willem Korthals | Nicolaes Witsen |