Masachi Osawa (?? ??, Osawa Masachi, born October 15, 1958 in Nagano, Japan) is a Japanese sociologist.
He received his Ph.D in Sociology from the University of Tokyo in 1990.
His Ph.D thesis is The Algebra of Actions (??????, Koi no Daisugaku).
His supervisor was Munesuke Mita.
He is one of the most influential sociologists in Japan and a prolific author.
He has taught at Chiba University and Kyoto University.
He has contributed to the most influential Japanese postmodern journal Critical Space (????, Hihyokukan), edited by Kojin Karatani and Akira Asada.
Outside Japan, he is best known as a social scientist, often mentioned in reference to sociological and philosophical research on otaku culture and popular Japanese animation series such as Ghost in the Shell: Stand Alone Complex.