Mary Winifred Aitken (née Betts; 11 May 1894 – 29 April 1971) was a New Zealand botanist. She was the first female lecturer at the University of Otago.^[1]

Born in Nelson on 11 May 1894, Betts was the daughter of printer and stationer Alfred George Betts and Ada Betts (née Grindley).^[1][2] Known to friends as Winnie, she was educated at Nelson College for Girls and received her Bachelor of Science (1916) and Master of Science (1917)^[3] degrees from the University of Otago. On her graduation, she received the National Research Scholarship that was awarded at the university each year, which offered her an income of £100 a year, plus lab expenses, so she could conduct independent research.

Betts was appointed university lecturer in botany in 1920 at age 25, the first woman to earn that designation.^[4] She was described by the pre-eminent botanist Leonard Cockayne as “the most brilliant woman scientist in New Zealand".^[3][4]

Also in 1920, she married another Otago graduate, the mathematician Alexander Aitken, and the couple remained in New Zealand as Winnie Aitken continued her botany lectures until 1923.^[4] In December 1923, the couple moved to Scotland so her husband could pursue his academic career; subsequently, he was named professor of mathematics at the University of Edinburgh.^[4][5]

Winifred Aitken died in Edinburgh on 29 April 1971.^[6]

In 2017, Betts was selected as one of the Royal Society of New Zealand's "150 women in 150 words".^[7]