Born in Drummondville, Quebec of Abenaki descent, Rita Letendre studied at the École des Beaux-Arts in Montreal in 1948, where the rigid methodology and conservative environment was ill-suited to her interest in creative exploration. In Montreal however she was exposed to the work of Paul-Émile Borduas, Jean-Paul Mousseau and Marcelle Ferron, with whom she was more sympathetic and creatively allied. She sought them out - they were showing in homes and apartments at the time - and in them, together with Ulysse Comptois, with whom she shared a studio for many years, and Gilles Groux, she found her contemporaries. "I was convinced I was going to revolutionize the universe," she stated in an interview with The Montrealer in 1962. She showed her work with the Automatists in 1952, 1953 and 1955, and in 1954 was included in the pivotal exhibition La matière chante, organized by Borduas. This lead to her inclusion in the important show Espace 1955 that was held at the Montreal Museum of Fine Arts. By the late 1950s, she had begun to show in New York, at both Parma Gallery and Canada House, and in 1959 her work was included in The Third Biennial Exhibition of Canadian Art at the National Gallery of Canada. In 1960, the NGC organized the exhibition Non-Figurative Artists of Montreal, which travelled to other venues in Canada and solidified Letendre's place in the forefront of Canadian non-figurative abstraction. Several other important shows followed, including several annual exhibitions at the Montreal Museum of Fine Arts and her first solo show which was held at the Here and Now Gallery in Toronto. Letendre has won numerous important painting prizes in Montreal including the Young Painters Prize in 1959 and the Rodolphe de Repentigny Prize in 1960, as well as the Province of Quebec Award in 1962. In Canada, her recognition is wide, and her international reputation reaches to Japan and France. She is an officer of the Order of Canada and was awarded the Governor General's Award for Visual Arts in 2010 and the Queen Elizabeth Diamond Jubilee Medal in 2012.

Letendre's early works are loosely handled and use repeating geometric forms that explore ideas of space and movement through dynamic, emotionally charged colour. She moved into hard-edge works in the style of Les Plasticiens as she matured, and explored very large format works through numerous public commissions, which include the 60 x 60 foot mural Sunrise (1971) at Ryerson University in Toronto. In the 1970s she began using an airbrush, which allowed her to achieve a subtle, even texture and gave her superb control that no other method of application allowed. This technique and her interest in hard-edge work led to her lithographic and screen prints. More recently, she has worked in pastel and returned to gestural painting, and she continues to paint and show work from her home in Toronto. Her work can be found in numerous public collections including the National Gallery of Canada, the Art Gallery of Ontario, the Montreal Museum of Fine Arts, the Musée du Quebec and the Vancouver Art Gallery.