Mariana Simionescu (born 27 November 1956) is a former professional tennis player from Romania. She played on the WTA Tour from 1973 to 1980. She won one WTA tour singes title at the Tokyo Outdoors in 1980. Her best Grand Slam performance was reaching the 4th round at Wimbledon in 1977 and she was ranked as high as 7 by the WTA. She won the French Open - Girls Singles title in 1974.
Simionescu was born in Târgu Neamț. She married Björn Borg in 1980, but the marriage ended in 1984. She has since remarried.