(William) Denis Johnston (18 June 1901 – 8 August 1984) was an Irish writer. Born in Dublin, he wrote mostly plays, but also works of literary criticism, a book-length biographical essay of Jonathan Swift, a memoir and an eccentric work on cosmology and philosophy. He also worked as a war correspondent, and as both a radio and television producer for the BBC. His first play, The Old Lady Says "No!", helped establish the worldwide reputation of the Dublin Gate Theatre; his second, The Moon in the Yellow River, has been performed around the globe in numerous productions featuring such storied names as James Mason, Jack Hawkins, Claude Rains, Barry Fitzgerald, James Coco and Errol Flynn. Later plays dealt with the life of Swift, the 1916 Rebellion, the pursuit of justice, and the fear of deat