Williamina Paton Stevens Fleming (May 15, 1857 – May 21, 1911), astronomer, was born in Dundee, Scotland, to Robert Stevens and Mary Walker Stevens. She attended public schools in Dundee, and at the age of 14, she became a pupil-teacher. She married James Orr Fleming, and they moved to the US and settled in Boston, Massachusetts, when she was 21. While pregnant with her son, Edward, her husband abandoned her, and she had to find work to support herself and Edward.

She worked as a maid in the home of Professor Edward Charles Pickering. Pickering became frustrated with his male assistants at the Harvard College Observatory and famously declared his maid could do a better job.

So in 1881, Pickering hired Fleming to do clerical work at the observatory. While there, she devised and helped implement a system of assigning stars a letter according to how much hydrogen could be observed in their spectra. Stars classified as A had the most hydrogen, B the next most, and so on.

Annie Jump Cannon improved upon this work to develop a simpler classification system based on temperature. Fleming contributed to the cataloguing of stars that would be published as the Henry Draper Catalogue. In nine years, she catalogued more than 10,000 stars. During her work, she discovered 59 gaseous nebulae, over 310 variable stars, and 10 novae. In 1907, she published a list of 222 variable stars she had discovered.

She was placed in charge of dozens of women hired to do mathematical classifications and edited the observatory's publications. In 1899, Fleming was given the title of Curator of Astronomical Photographs. In 1906, she was made an honorary member of the Royal Astronomical Society of London, the first American woman to be so elected. Soon after, she was appointed honorary fellow in astronomy of Wellesley College. Shortly before her death, the Astronomical Society of Mexico awarded her the Guadalupe Almendaro medal for her discovery of new stars.

She died in Boston of pneumonia.