Nishiyama Sōin (西山 宗因?, born Nishiyama Toyoichi (西山 豊一) March 28, 1605 in Higo Province, Japan – May 5, 1682 in Kyoto) was a haikai-no-renga poet of the early Tokugawa period. He founded the Danrin school of haikai poetry, which aimed to move away from the serious 'bookishness' popular in Japanese poetry at the time and become more in touch with the common people, infusing a spirit of greater freedom into their poetry.
Sōin's haikai (comical renga) became the transition between the light and clever haikai of Matsunaga Teitoku and the more serious and aesthetic renku of Matsuo Bashō.