Keiiti Aki (March 3 1930 - May 17 2005) was a professor, seismologist, author and mentor. He co-authored with Paul Richards, "Quantitative Seismology: theory and methods".

Aki was very active in his field and was the president or chair of many organizations. He was the president of Seismological Section of the AGU, president of the Seismological Society of America, and Chair of the NAS Committee on Seismology. He was instrumental in the creation of the Southern California Earthquake Center in 1991.