Mayumi Ohkutsu (; born July 12, 1968 in Obihiro, Hokkaido, Japan as Mayumi Seguchi; also known as Mayumi Seguchi-Ohkutsu, Mayumi Seguchi-Okutsu) is a Japanese curler, a five-time (1991, 1993, 1995, 1996, 1997) and a six-time Japan women's champion (1991, 1992, 1993, 1996, 1997, 1998).