Lilian Helen Alexander (15 March 1861 – 18 October 1934) was an Australian surgeon and one of the first women to study medicine at the University of Melbourne.
Alexander was born in 1861 at St Kilda, Victoria to Jane and Thomas Alexander. Her father was an English-born printer while her mother was an Irish-born school administrator. She attended Lawn House, the school run by her mother, and Presbyterian Ladies' College before enrolling at the University of Melbourne. She graduated with a Bachelor of Arts in 1886 and a Master of Arts in 1888 and was the first female student admitted to the university's Trinity College, "against considerable opposition", making her the first woman to be admitted to any Australian university's residential college. After graduating, Alexander worked as a schoolteacher at Ruyton Girls' School.
In 1887, after she and Helen Sexton petitioned the university, Alexander became one of the first five women to be admitted to the University of Melbourne Faculty of Medicine. She received her Bachelor of Medicine in 1893, becoming a qualified medical doctor, and completed her medical residency at the Royal Women's Hospital in Carlton.
Alexander was involved in the formation of the Queen Victoria Hospital for Women and Children (now Monash Children's Hospital) and was one of the hospital's original staff members alongside Constance Stone and a number of other recent female medical graduates. Alexander specialised in surgery after gaining her Bachelor of Surgery in 1901, and worked at the Queen Victoria Hospital until 1917. She practised medicine privately until 1928. In 1931, she was elected president of the Victorian Medical Women's Society after serving as the society's first secretary since 1896.