Momo Koseki (???, Koseki Momo, born July 31, 1982) is a Japanese former professional boxer.
She is a two-weight world champion, having held the WBC female atomweight title from 2008 to 2015; the WBA female atomweight title in 2015; and the WBC female minimumweight title in 2017.
Koseki has made a record-breaking sixteen consecutive title defenses of her WBC atomweight title.