Wakai (written: 若井) is a Japanese surname. Notable people with the surname include:
Atsuko Wakai (若井 敦子, born 1971), Japanese karateka
Glenn Wakai (born 1967), American politician
Kenji Wakai (若井 研治, born 1974), Japanese footballer
Atsuko Wakai (若井 敦子, Wakai Atsuko, born 1971) Japanese practitioner
Wakai ki (若い樹) (lit. 'A Young Tree') Japanese film directed
