Mary Hildegard Ruth Bauermeister (7 September 1934 – 2 March 2023) was a German artist who worked in sculpture, drawing, installation, performance, and music.

Beginning in the 1970s, her work concentrated on the themes surrounding New Age spirituality, specifically geomancy, the divine interpretation of lines on the ground.

These activities have been described as "comparatively non-hierarchical exchanges of information across national, disciplinary and age boundaries", contributing in that way to the character of the Fluxus movement which had been developing during the 1950s.

[11] Later that same year she collaborated with Stockhausen in a theatre piece titled Originale (Originals), which was given twelve performances at the Theater am Dom, Cologne, from 26 October to 6 November 1961.

[12] In 1962 she had her first solo exhibition at the Stedelijk Museum in Amsterdam with a simultaneous day-long performance of electronic music under Stockhausen's direction.

In the artistic circles of Pop Art, Nouveau Réalisme, and Fluxus, she maintained friendships with Robert Rauschenberg, Jasper Johns, Niki de Saint Phalle, and Jean Tinguely.

[10] On the occasion of her 70th birthday in September 2004, the Cologne Museum Ludwig acquired her 1963 wall installation Needless Needles and arranged a display of the work for several months.

[4] In 2019, Museum Ludwig acquired three more works by Bauermeister, Rundes Wabenbild, Magnetbild Schwarz-Weiss, and the relating 34 sketches Möglichkeiten Serieller Malerei.