Wilhelm Mach, pen names il., Quidam, s., S., Współpracownik ( 26 December 1916,[a] Kamionka - 2 June 1965 in Warsaw) was a Polish writer, essayist, poet and literary critic.

He debuted with a poem Jesień (Autumn) printed in a school press Przyszłość (Future, issue from 1 September 1928) and a novella Dawne zapusty published in a timely Rola.

During the occupation, he lived with his sister Bronisława in the Księżomost part of Sędziszów Małopolski, and then from 1941 in Kraków, where he worked at the Social Insurance Institution (Ubezpieczalnia Społeczna).

Wilhelm Mach himself considered his literary debut the publication of the poem Tobie dalekiej (To distant you), printed in autumn 1945 in a one-day journal Inaczej (Differently), co-redacted by him.

In 1950–1958 he was the editor of the weekly Nowa Kultura (New culture), where he became known as a patron of aspiring and beginning writers, reviewing their works and advertising them to the publishers.

[1] Literary friends of Mach, such as Marek Nowakowski [pl]and Kazimierz Brandys, however, recalled that the writer committed suicide by poisoning himself and that he talked about such plans even earlier.

[1] Nowakowski would later describe how Mach shared the fate of many Polish gay men of the period, having to hide in the closet and live a double life, looking for relationships in shady surroundings such as train stations.