Ōsawa, Osawa or Oosawa (written: 大沢 or 大澤 lit. "big swamp") is a Japanese surname. Notable people with the surname include:

• Chiho Osawa (大澤 ちほ, born 1992), Japanese ice hockey player
• Eiji Osawa (born 1935), Japanese chemist
• Itsumi Osawa (born 1966), Japanese actress, writer and singer
• Kenji Osawa (born 1976), Japanese mixed martial artist
• Kisaburo Osawa (1910–1991), Japanese aikidoka
• Masaaki Ōsawa (born 1946), Japanese politician and governor of Gunma Prefecture
• Masayo Ōsawa (1913–1945), Japanese diver
• Masayuki Osawa (大沢 正行, born 1946), Japanese swimmer
• Reiko Ōsawa (born 1915), Japanese diver
• Shigeki Osawa (born 1986), Japanese mixed martial artist
• Shinichi Osawa (born 1967), Japanese musician better known as Mondo Grosso
• Takao Osawa (born 1968), Japanese actor

See also

• 19310 Osawa, an asteroid
• Ōsawa Station (disambiguation)
• Ozawa