Hiroo Kanamori (金森 博雄 Kanamori Hiroo^?, October 17, 1936 –) is a Japanese American seismologist who has made fundamental contributions to understanding the physics of earthquakes and the tectonic processes that cause them.

Kanamori and American seismologist Tom Hanks developed the moment magnitude scale which replaced the Richter magnitude scale as a measurement of the relative strength of earthquakes.

Kanamori invented the method for calculating slip distribution on the fault plane by teleseismic waveform with Masayuki Kikuchi. In addition, they studied realtime seismology.

In 2007 he was awarded the Kyoto Prize in Basic Sciences.