Islwyn Ffowc Elis (Welsh pronunciation: [ˈɪslʊɨn fɔʊk ˈɛlɪs]; 17 November 1924 – 22 January 2004) was one of Wales's most popular Welsh-language writers.
Born Islwyn Ffoulkes Ellis in Wrexham and raised in Glyn Ceiriog, Elis was educated at the University of Wales colleges of Bangor and Aberystwyth.
He made his debut as a novelist in 1953 with Cysgod y Cryman (translated into English as Shadow of the Sickle), which would, in 1999, be chosen as the most significant Welsh language book of the 20th century.
Later works included Y Blaned Dirion (The Meek Planet 1968, another science fiction novel), Y Gromlech yn yr Haidd (The Dolmen in the Barley, 1971) and Eira Mawr (Great Snow, 1972).
In 2021, his novel Wythnos yng Nghymru Fydd that was translated into English by Stephen Morris (in 2019) was published as A Week in Future Wales by Cambria Futura.