Kerstin Fredga (born 1935) is a Swedish astronomer and spectroheliographer whose research involves the spectra of the sun and other stars. She is the former director of the Swedish National Space Agency and former president of the Royal Swedish Academy of Sciences.

Fredga was born in Stockholm in 1935, one of five children of chemistry professor Arne Fredga [sv] and his wife, a kindergarten teacher, who encouraged her to pursue her interest in astronomy. After studies at Uppsala University, she completed a Ph.D. in astronomy in 1962.^[1]

She began her career working at the Institute for Solar Physics on Capri. After continued research on rocket-based ultraviolet solar observation at the Goddard Space Flight Center in the US, and in the Astronomical Institute and Space Research Laboratory of the University of Utrecht, she returned to Sweden, and in 1973 became a professor at Stockholm University, at the same time moving from research towards academic administration in the Swedish National Space Agency. She was project scientist for Viking, Sweden's first satellite, which launched in 1986,^[2] and directed the agency for ten years beginning in 1989.^[1] She has also chaired the Space Science Council of the European Space Agency.^[3]

Fredga was elected to the Royal Swedish Academy of Sciences in 1978, and later became its president.^[1][3] She was also elected to the Royal Swedish Academy of Engineering Sciences in 1986, and to the Academia Europaea in 1988.^[3]

She was the 1983 recipient of the KTH Great Prize of the KTH Royal Institute of Technology, citing "her broad knowledge in astronomy and space physics as well as experiences from American space projects".^[4]