William Butler Yeats was a renowned Irish poet who lived from 1865 to 1939. He is considered one of the greatest poets of the 20th century and was awarded the Nobel Prize in Literature in 1923. Yeats was heavily influenced by the culture of his native Ireland, as well as the ancient city of Byzantium, which he often wrote about in his works. His most famous poem, 'Sailing to Byzantium, ' is a reflection on mortality and the search for immortality.