Helga Niessen Masthoff (née Niessen; born 11 November 1941) is a retired tennis player from West Germany. Her best Grand Slam singles tournament was when she reached the 1970 French Open final, losing to Margaret Court in straight sets. She won the German Open three consecutive years from 1972 through 1974, beating Martina Navratilova in the 1974 final in three sets. Masthoff was the runner-up at that tournament in 1971, losing to Billie Jean King. She won the German national singles title on ten occasions (1965, 1966, 1968, 1969, 1971, 1972, 1975, 1976, 1977 and 1978).