Helena Charlotta Westermarck (20 November 1857, Helsinki – 5 April 1938, Helsinki) was a Swedish-speaking Finnish artist and writer. She was the sister of Edvard Westermarck. She worked for long periods in France, often in the company of Helene Schjerfbeck, and developed a sensible realistic style especially with portraits and figure compositions. At the Exposition Universelle (1889), she received honorable mention for her painting Strykerskor. Then she abandoned painting and devoted herself to writing as a critic. Westermarck also made a significant contribution as a researcher through her cultural and historical works, among which are a series of biographies of female figures, Mathilda Rotkirch (1926), Adelaide Ehrnrooth (1928), and Rosina Heikel (1930). Westermarck's memoir was published in 1941.