Nagai (written: 永井 lit. eternal well or 長井 lit. "long well") is a Japanese surname. Notable people with the surname include:
, Japanese boxer Go Nagai, Japanese manga artist Hazuki Nagai (born 1994), Japanese field hockey player , a member of K-Pop girl group, LIGHTSUM Jordan Nagai (born 2000), American former voice actor Jun Nagai (born 1944), Japanese middle-distance runner Kafū Nagai, Japanese novelist, playwright, essayist, and diarist Kazumasa Nagai (1929–2026), Japanese printmaker and graphic designer Kenji Nagai, Japanese journalist, killed in Myanmar Kensuke Nagai, Japanese footballer Koji Nagai, Japanese businessman, CEO of Nomura Holdings Koji Nagai (baseball), Japanese baseball coach Michiko Nagai, Japanese writer , Japanese mixed martial artist, kickboxer and professional wrestler , Japanese samurai Ryo Nagai, Japanese footballer , Japanese footballer Takashi Nagai, Japanese radiologist and Catholic writer Tatsuo Nagai, Japanese writer Yasutomo Nagai (1965–1995), Japanese motorcycle racer Yuri Nagai (born 1992), Japanese field hockey player