Rolf Maximilian Sievert (Swedish: ['r?lf maks?'mi?l?an 'si?v??]; 6 May 1896 – 3 October 1966) was a Swedish medical physicist whose major contribution was in the study of the biological effects of ionizing radiation.
Sievert was born in Stockholm, Sweden.
He served as head of the physics laboratory at Sweden's Radiumhemmet from 1924 to 1937, when he became head of the department of radiation physics at the Karolinska Institute.
He played a pioneering role in the measurement of doses of radiation especially in its use in the diagnosis and treatment of cancer.
In later years, he focused his research on the biological effects of repeated exposure to low doses of radiation.
In 1964, he founded the International Radiation Protection Association, serving for a time as its chairman.