Llewelyn Wyn Griffith (30 August 1890 – 27 September 1977) was a Welsh novelist, born in Llandrillo yn Rhos, Clwyd. A captain in the 15th Royal Welch Fusiliers during First World War, he is best known for his memoir, Up to Mametz, which he wrote in the early 1920s, although the work was not published until 1931.