Marjorie Jackson was born in Coffs Harbour, New South Wales, and first gained fame when she defeated reigning Olympic 100 and 200 metres champion Fanny Blankers-Koen a number of times in 1949, thus earning the nickname "the Lithgow Flash", after the New South Wales town of Lithgow where she lived and had grown up.
Having won four titles at the 1950 British Empire Games, Jackson came as a favourite to the Helsinki 1952 Summer Olympics. She won both the 100 m, in a then-world-record-equalling time of 11.5, and the 200 m, winning the first Olympic athletics track titles for Australia since Edwin Flack in 1896. Having more strong runners in the team, the Australian 4 × 100 m relay team was also a favourite for the gold, but a faulty exchange meant Jackson's chances for third gold medal were gone. The Americans, anchored by Catherine Hardy (later Lavender), won in an upset, setting a new world record time of 45.9 seconds. Later in 1952, Jackson lowered the 100 m world record time to 11.4, running this new record in a meet at Gifu, Japan on 4 October 1952.
In 1953 Jackson married Olympic cyclist Peter Nelson. After his death from leukaemia in 1977, she launched the Peter Nelson Leukaemia Research Fellowship. Now named Jackson-Nelson, she was one of the eight flag-bearers of the Olympic Flag at the opening ceremony of the 2000 Summer Olympics in Sydney. She also has a road named in honour of her at the Sydney Olympic Park, beside the Sydney Superdome (now Allphones Arena).