Masao (written: 正雄, 正夫, 正生, 正男, 正郎, 雅雄, 雅央, 雅夫, 雅勇, 雅男, 昌雄, 昌夫, 昌男, 昌朗, 昌郎, 昌大, 政雄, 政夫, 政男, 政於, 征夫, 優夫, 聖雄, 利生, 将雄, 将夫 or 眞男) is a masculine Japanese given name. Notable people with the name include:

• Masao Abe (阿部 正雄, 1915–2006), Japanese philosopher and writer
• Masao Adachi (足立 正生, born 1939), Japanese screenwriter and film director
• Masao Akamatsu (赤松 正雄, born 1945), Japanese politician
• Amatsukaze Masao (天津風 征夫, 1937–2013), Japanese sumo wrestler
• Masao Arai (荒井 政雄, born 1949), Japanese sport wrestler
• Masao Azuma (東 雅雄, born 1971), Japanese motorcycle racer
• Baba Masao (馬場 正郎, 1892–1947), Japanese general
• Masao Doi, Japanese academic
• Masao Fujii (藤井 将雄, 1968–2000), Japanese baseball player
• Masao Gozu (郷津 雅夫, born 1946), Japanese photographer and sculptor
• Inaba Masao, Japanese military officer and rebel
• Masao Haji (土師 政雄, 1925–1998), Japanese activist and academic
• Masao Harada (原田 正夫, 1912–2000), Japanese triple jumper
• Masao Horino (堀野 正雄, 1907–2000), Japanese photographer
• Masao Ichihara (市原 正雄, 1913–1977), Japanese sprinter
• Masao Inoue (actor) (井上 正夫, 1881–1950), Japanese actor and film director
• Masao Inoue (wrestler) (井上 雅央, born 1970), Japanese professional wrestler
• Masao Ito (伊藤 正男, born 1928), Japanese neuroscientist
• Masao Iwasato (岩里 政男, born 1923), former President of the Republic of China (Taiwan)
• Masao Kanamitsu (1943–2011), Japanese American meteorologist
• Masao Kato (加藤 正夫, 1947–2004), Japanese Go player
• Masao Kawai (河合 雅雄, born 1924), Japanese primatologist
• Masao Kiba (木場 昌雄, born 1974), Japanese footballer
• Masao Kida (木田 優夫, born 1968), Japanese baseball player
• Masao Kinoshita (木下 政雄), Japanese businessman
• Masao Kitagawa (北川 政夫, 1910–1995), Japanese botanist
• Kiyonomori Masao (清の盛 政夫, 1935–2019), Japanese sumo wrestler
• Masao Kobayashi (小林 正夫, born 1947), Japanese politician
• Masao Koga (古賀 政男, 1904–1978), Japanese composer and guitarist
• Masao Komatsu (小松政夫, 1942–2020), Japanese actor
• Masao Kotani (小谷 正雄, 1906–1993), Japanese theoretical physicist
• Masao Kume (久米 正雄, 1891–1952), Japanese playwright, writer and poet
• Masao Maeda (前田 政雄, 1904–1974), Japanese printmaker
• Masao Maruyama (film producer) (丸山 正雄, born 1941), Japanese animator and film producer
• Masao Maruyama (Japanese Army officer) (丸山 政男, 1889–1957), Japanese general
• Masao Maruyama (scholar) (丸山 眞男, 1914–1996), Japanese political scientist and historian
• Masao Mimatsu (三松 正夫, 1888–1977), Japanese volcanologist
• Masao Miyamoto (宮本 政於, 1948–1999), Japanese psychiatrist
• Masao Miyoshi (三好 将夫, 1928–2009), Japanese sociologist
• Masao Morinaka (森中 聖雄, born 1974), Japanese baseball player
• Masao Mukai (向井 正雄, born 1958), Japanese conductor
• Masao Murano (村野 正夫, born 1935), Japanese ice hockey player
• Masao Murata (村田 正夫, born 1964), Japanese judoka
• Masao Nakabori (中堀 正夫), Japanese cinematographer
• Masao Nakamura (中村 正雄, 1892–1939), Japanese general
• Masao Nakayama (中山 利生, 1941–2011), Japanese politician and diplomat
• Masao Nozawa (野澤 正雄), Japanese footballer
• Masao Ohba (大場 政夫, 1949–1973), Japanese boxer
• Masao Ono (大埜 正雄, 1923–2001), Japanese footballer
• Masao Orihara (折原 昌夫, born 1969), Japanese professional wrestler
• Masao Sasakibara (佐々木原 正夫, 1921–2005), Japanese World War II flying ace
• Masao Sen (千 昌夫, 1947), Japanese singer
• Masao Shimizu (清水 将夫, 1908–1975), Japanese actor
• Masao Suenaga (末永 正雄, born 1978), Japanese drifting driver
• Masao Sugimoto (born 1967), Japanese footballer
• Masao Sugiuchi (杉内 雅男, born 1920), Japanese Go player
• Masao Takada, Japanese footballer
• Masao Takagi (高木 正雄, 1917–1979), former President of South Korea
• Masao Takahashi (born 1929), Canadian judoka
• Masao Takemoto (竹本 正男, 1919–2007), Japanese artistic gymnast
• Masao Takenaka (1925–2006), Japanese theologian
• Masao Takiyama (滝山 正夫), Japanese television producer
• Masao Tsuchida, Japanese baseball player
• Masao Tsukada (塚田 正夫, 1914–1977), Japanese shogi player
• Masao Uchino (内野 正雄, born 1934), Japanese footballer and manager
• Masao Urino (売野 雅勇, born 1951), Japanese lyricist, screenwriter and film director
• Masao Watanabe (渡辺 正夫, 1888–1950), Japanese general
• Masao Yagi (八木正生, 1932–1991), Japanese jazz musician
• Masao Yamaguchi (山口 昌男, 1931–2013), Japanese anthropologist
• Masao Yamamoto (山本 昌男, born 1957), Japanese photographer
• Masao Yoshida (disambiguation), multiple people