Kyogoku was born in Hiroshima, Japan, the daughter of Itsuzo Kyogoku and Kiyo Kyogoku. Her family moved to the United States in 1919, after her father, a Buddhist priest, was assigned to serve Buddhists in California.[2] She lived in Lompoc as a teenager,[3] and graduated from the University of California, Berkeley with a BA in home economics in 1938.[4][5]
While in Philadelphia, Hasegawa began work with the Women's International League for Peace and Freedom (WILPF), a peace-seeking non-governmental organization that had vehemently opposed the internment of Japanese Americans and helped to relocate and readjust freed Japanese. She would hold varying roles within WILPF for the next fifty years, such as the chair of its Membership and Extension Committee from 1960 to 1965, its consultant to committees from 1965 to 1968, and its national president from 1971 to 1975.[8] Her presidency of the organization was during the Vietnam War. Hasegawa organized protests against the war and led a peace delegation to North Vietnam.[4][9][10]
She moved to South Hadley, Massachusetts in 2001, where she continued to be active in working for peace and inter-religious cooperation until her death on July 1, 2012. In 2012, a documentary, Marii Hasegawa: Gentle Woman of a Dangerous Kind, was shown at film festivals.[12] She was named one of the Library of Virginia's Virginia Women in History in 2018.[13]
