Islwyn Ffowc Elis (Welsh pronunciation: [ˈɪslʊɨn foʊk 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. During World War II he was a conscientious objector and he began writing poetry and prose, winning the prose medal at the 1951 National Eisteddfod. He became a Presbyterian minister in 1950, and his first pastorate was at Moreia Chapel in Llanfair Caereinion. 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.
As a novelist Elis showed a great willingness to try out different forms, including popular ones. Cysgod y Cryman was followed by a study of intellectual decadence, Ffenestri tua'r Gwyll (Windows to the Dusk 1955). Yn ôl i Leifior (1956; translated into English as Return to Lleifior) was a sequel to Cysgod y Cryman both set at the fictitious farming location Lleifior. In 1957, the Welsh nationalist party Plaid Cymru published his time-travel story Wythnos yng Nghymru Fydd (A Week in Future Wales), presenting an independent, utopian Wales and a dystopian "Western England" in alternative versions of 2033. Blas y Cynfyd (A Taste of Prehistory 1958) was followed by the colonial satire Tabyrddau'r Babongo (Drums of the Babongo 1961). He thus pioneered the use of genres unfamiliar to Welsh-speaking readers, provided them with a highly readable prose often set in contemporary settings, and did much to establish the position of the novel as a major genre in Welsh-language literature. For periods he set out to live off his writing, something hardly attempted before in modern Welsh.