Sugai (written: 菅井 or 須貝) is a Japanese surname. Notable people with the surname include:
*, Japanese singer, composer and arranger
*, Japanese judoka
*, Japanese actor
*, Japanese actress
*, Japanese painter and printmaker
*, Japanese ballet dancer
*, Japanese footballer
*, Japanese golfer
*, Japanese dermatologist
*, Japanese footballer
*, Japanese shogi player
*, Japanese long jumper
*, Japanese idol singer
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Japanese-language surnames