Ōsawa, Osawa or Oosawa (Japanese: 大沢 or 大澤, lit. "big swamp") is a Japanese surname. Notable people with the surname include:
Chiaki Ōsawa (born 1981), a Japanese voice actress
Eiji Osawa (born 1935), a former professor of computational chemistry noted for his prediction of the C60 molecule molecule in 1970
Itsumi Osawa (born 1966), a Japanese actress, author, and singer
Kenji Osawa (born 1976), a retired Japanese mixed martial artist
Kisaburo Osawa (1910–1991), a former aikido teacher who taught at Aikikai Hombu Dojo
Masaaki Ōsawa (born 1946), a Japanese politician and governor of Gunma Prefecture
Masayo Ōsawa (1913–1945), a Japanese diver who competed in the 1936 Summer Olympics and finished sixth in the women's 3 m springboard and 14th in the 10 m platform competition
Reiko Ōsawa (born 1915), a Japanese diver who competed in the 1936 Olympics and finished fourth in the 10 m platform event
Shigeki Osawa (born 1986), a Japanese professional mixed martial artist who competes in the featherweight division
Shinichi Osawa (born 1967), a Japanese musician better known as Mondo Grosso
Takao Osawa (born 1968), a Japanese actor
