Marianne Gast was a German photographer. She specialised in photographing architecture and works of art. For many years she was the primary photographer of works by the German-born artist Mathias Goeritz, her husband from 1942 to 1958. The majority of her archive is now held by the National Institute of Fine Arts in Mexico; other documents are held by the Lafuente Archive. In 2018 the first solo exhibition of Gast's work was displayed at the Centro de Documentación de la Imagen in Santander, Spain.
Gast was born in Schierke, Germany, and educated in England and France. During this period she began to practice photography. In 1942 she met the German-born painter and sculptor Mathias Goeritz in Tangier, when both were working at the Deutsche Akademie. They married the same year, and settled in Spain after the Second World War, living first in Granada, then Madrid. In 1948, the couple moved to Santillana del Mar because Gast had been commissioned to take photographs for a planned book on the town.
In 1949, Gast and Goeritz moved to Mexico, as Goeritz had been invited to teach at the new school of architecture in Guadalajara.