Mary Cecil Allen (2 September 1893 – 7 April 1962) was an Australian artist, writer and lecturer. She lived most of her adult life in America, where she was known as Cecil Allen. Allen initially painted landscapes and portraits in her early career, but changed to modernist styles including cubism from the 1930s. In 1927 Allen lectured at New York City venues including the Metropolitan Museum, Columbia University and other institutions. She was sponsored by the Carnegie Corporation. Allen wrote two books of art criticism, The Mirror of the Passing World (1928) and Painters of the Modern Mind (1929), based on her lectures.

In 1930 Allen curated the first exhibition of Australian art in New York, "First Contemporary All-Australian Art Exhibition", at the Roerich Museum. During her lectures and talks in Australia, she helped introduce the ideas of modernism to Melbourne women and artists. After living in New York, from 1949 Allen lived in Provincetown at its art colony. Her cubist style painting, "Sea, studio: Winter", was presented in that year. She died in 1962, at the colony, from "sinus arrest, cause unknown" (see sinoatrial arrest).

Allen was the daughter of Harry Brookes Allen (1854–1926), a pathologist and medical administrator, and Ada Rosalie Elizabeth, née Mason (1862–1933), a community worker. She and her sisters, Edith Margaret and Beatrice (Biddy), spent their childhood living in a staff house at the University of Melbourne where their father was an anatomy professor and the Dean of Medicine. Her father was knighted in 1914. Allen qualified to study a Bachelor of Arts at the University of Melbourne, but decided to study under Fred McCubbin at the National Gallery of Victoria Art School instead, entering the faculty of arts in 1910. From 1912 to 1913 Allen studied at the Slade School of Fine Art when she and her family moved to England. She returned to NGV Art School during 1913–17.

Allen was a member of Australian Art Association, the Victorian Artists' Society and the Twenty Melbourne Painters during the 1920s and her exhibitions of landscapes and portrait paintings were well received by the Melbourne art world. She was also a member of society, being friends with Ivy Brookes (daughter of Alfred Deakin) and having Dame Nellie Melba and University Vice-Chancellor Sir John Grice open some of her exhibitions. Two of Allen's portraits were finalists in the Archibald Prize in 1921 and a further two were finalists in 1925. During early September 1921 Allen exhibited a set of fifty-four oil paintings at the Fine Art Society's Gallery in Melbourne. In 1925 Allen became the first woman art critic for The Sun. She studied under Max Meldrum, a tonal impressionist whose students, Arnold Shore and Jock Frater, had been experimenting with modernism. At this point, Allen was not yet a fan of modernism — she criticised Shore's work in The Sun and said that post-impressionists "create nothing but monsters–they invent the abnormal" during one of her lectures. In 1926 she was employed by the National Gallery of Victoria as an art guide and lecturer — the first woman to hold this position.

In 1926, Florence Gillies, an American tourist, visited Melbourne and invited Allen to be her guide through European galleries, mostly in Paris. Following this, in 1927, Allen lectured at New York City venues including the Metropolitan Museum, Columbia University and other institutions. She ran a series of lectures at the Readers Roundtable of the People's Institute, held at the New York Public Library, where newly created adult classes were taking place and were sponsored by the Carnegie Corporation. From that time, Allen generally lived and worked in New York. According to Marion Scott "[Allen] was able to increase one's ability to comprehend visually what had previously been puzzling... She did this by using words with great economy, words which were so lucid that they created no barrier between one's eyes and the work of Art."

Following her work and travels in Europe and America, Allen converted to modernism. She wrote two books, The Mirror of the Passing World (1928) and Painters of the Modern Mind (1929) based on her lectures and in the latter book, stated "that art should convey ideas, rather than mimic visual reality".

In 1930 Allen organised the first exhibition of Australian artists in New York, "First Contemporary All-Australian Art Exhibition", at the Nicholas Roerich Museum, opening in February 1931. Besides her own work, featured artists included Norman Lindsay, Thea Proctor, George Bell and Dora Toovey: and one hundred paintings were shown. The cover of the exhibition catalogue had the Commonwealth coat of arms and a notice of patronage by Prime Minister James Scullin. Herbert Brookes, husband of Allen's friend Ivy, had been the Commissioner General for Australia in the United States from 1929 to 1930 and had approved the official stamp on the exhibition catalogue, adding the newly elected prime minister's name as his representative in New York.

The exhibition attracted large attendances and interest, and then Allen lectured on the works during its tour. La Revue Moderne, a French modern art journal, profiled her in 1931. The New York Times called her work in the Australian Art exhibition "arrestingly modern" — this was in contrast to the conservative works of other Australian artists. In a later interview with The Advertiser, on 17 June 1936, Allen mentioned all the art work exhibited had non-Australian scenery and had titles such as "Landscape in Spain" and "Bosky Dells in Surrey". She elaborated, "If I had come upon as much as a single kangaroo I would have hailed it with delight".