Home / English / What is Lyonnesse? English What is Lyonnesse? Posted on03/10/202212/09/2022 Updated on12/09/2022 Lyonnesse is the mythical birthplace of Sir Tristram, in England, believed to have been submerged by the sea. Related posts: Why did the poet visit a parish? On his return from the parish what two things did people notice about him? In which season did he set out on his journey for Lyonnesse? Who accompanied him in his loneliness?