Hamaguchi (written: or ) is a Japanese surname. Notable people with the surname include:
, Japanese basketball player , Japanese basketball coach , Japanese volleyball player , Japanese skate boarder, invented the bicycle trick; "Ninja brakes", a dismount technique, running out of a bicycle at its top speed , Japanese comedian , 27th Prime Minister of Japan , Japanese film director and screenwriter , Japanese anime composer , Japanese footballer , Japanese motorcycle racer , Japanese freestyle swimmer