Hyakunin Isshu (one hundred waka poems by one hundred poets) is a poetry anthology containing one hundred waka (classical Japanese poems), one each by distinguished poets from ancient times; in the past, it had been called 'Hyakunin-shu.'
百人一首（ひゃくにんいっしゅ、故実読みはひゃくにんしゅ）とは、古来の代表的な歌人百人について、一人一首を選んでつくった詞華集のことである。