Llewellyn was born Vivian Lloyd of Welsh parents in Hendon, Middlesex, in 1906. Only after his death was it discovered that his claim that he was born in St. Davids, West Wales, was false.
He lived a peripatetic life, travelling widely throughout his life. Before World War II, he spent periods working in hotels, wrote a play, worked as a coal miner and produced his best-known novel. During World War II, he rose to the rank of Captain in the Welsh Guards. Following the war, he worked as a journalist, covering the Nuremberg Trials, and then as a screenwriter for MGM. Late in his life, he lived in Eilat, Israel.
Llewellyn married twice: his first wife was Nona Sonstenby, whom he married in 1952 and divorced in 1968, and his second wife was Susan Heimann, whom he married in 1974.
Richard Llewellyn died in London on 30 November 1983.
Several of his novels dealt with a Welsh theme, the best-known being How Green Was My Valley (1939), which won international acclaim and was made into a classic Hollywood film. It immortalised the way of life of the South Wales Valleys coal mining communities, where Llewellyn spent a small amount of time with his grandfather. Three sequels followed.
Llewellyn's novels often included the recurring element of protagonists who assume new identities (as they are transplanted into foreign cultures), such as the character Edmund Trothe whose adventures extends through several spy adventure books.
- Poison Pen: A Play in Three Acts (1938)
- How Green Was My Valley (1939)
- None but the Lonely Heart (1943)
- A Few Flowers for Shiner (1950)
- A Flame for Doubting Thomas (1954)
- Sweet Witch (1955)
- Mr. Hamish Gleave (1956)
- The Flame of Hercules (1957)
- Warden of the Smoke and Bells (1958)
- Chez Pavan (1959)
- Up into the Singing Mountain (1960)
- A Man in a Mirror (1964)
- Sweet Morn of Judas' Day (1965)
- Down Where the Moon is Small (1966)
- Bride of Israel My Love (1973)
- Hill of Many Dreams (1974)
- Green, Green My Valley Now (1975)
- At Sunrise, the Rough Music (1976)
- Tell Me Now and Again (1977)
- A Night of Bright Stars (1979)
- I Stand on a Quiet Shore (1982)
- Edmund Trothe series
- End of the Rug (1969)
- But We Didn't Get the Fox (1970)
- White Horse to Banbury Cross (1972)
- The Night is a Child (1974)
- "BBC Wales – Arts - Richard Llewellyn". BBC Cymru Wales website. BBC Cymru Wales. 28 November 2008. Retrieved 2010-04-05.
- Dictionary of National Biography "Lloyd, Richard Dafydd Vivian Llewellyn (1906–1983)" Check
|url=value (help). Sep 2004. Retrieved 2010-04-11.
- "True birthplace of Wales's literary hero". BBC News. BBC. 1999-12-05. Retrieved 2010-04-06.
- Ruthven, KK (2001). Faking Literature. Cambridge University Press. p. 13. ISBN 0-521-66015-7.
- Llewellyn , Richard , 1906-1983
- What appears to be his birth certificate gives his name as Richard Herbert V Lloyd, see http://www.freebmd.org.uk
- "Books and Authors", The New York Times, 16 February 1941, page BR12. ProQuest Historical Newspapers The New York Times (1851–2007).