Roberta Henrietta Margaritta Jull (née Stewart, 16 August 1872 in Glasgow, Scotland – 6 March 1961 in Subiaco, Western Australia) was a medical doctor who, in November 1896, joined her brothers' practice at Guildford, Western Australia, becoming dismayed by the living conditions and high infant mortality among her patients. In 1897, Jull became the first woman to establish a practice in Perth, Western Australia.
Jull took a leading part in improving the standard of women's and infant health services in the state and became a respected force and agitator for social reform. The next year she became a member of the influential Karrakatta Club as well as a founding member of the British Medical Association, Western Australian Branch.
Close associates included Edith Cowan, Lady Onslow, Lady Gwenyfred James and Janetta Griffiths-Foulkes. The group of well-connected and wealthy ladies actively petitioned the government for women's and social reform issues, establishing several reformist organisations.
In 1915 she married Martin Jull, Under Secretary for the Public Works Department and afterwards the state's first Public Service Commissioner for Western Australia. In 1916 she became a member of the Senate for the University of Western Australia.
She became chief medical officer for schools at the Western Australian Public Health Department in 1925 and in 1930 was a member of the Australian delegation to the League of Nations congress.