Kosugi (written: 小杉 lit. "small Japanese cedar" or コスギ in katakana) is a Japanese surname. Notable people with the surname include:
Isamu Kosugi (小杉 勇) (1904–1983), Japanese actor and film director
Jūrōta Kosugi (小杉 十郎太) (born 1957), Japanese voice actor
Kane Kosugi (ケイン・コスギ) (born 1974), American karateka and actor
Sho Kosugi (ショー・コスギ) (born 1948), Japanese karateka and actor
Shunji Kosugi (小杉 俊二) (born 1960), Japanese professional wrestler
Takashi Kosugi (小杉 隆) (born 1935), Japanese politician
Takehisa Kosugi (小杉 武久) (born 1938), Japanese classical composer
Kosugi Tengai (小杉 天外) (1865–1952), pen-name of Kosugi Tamezō, Japanese writer
Toshiyuki Kosugi (小杉 敏之) (born 1968), Japanese footballer
