Mary Clarissa "May" Byron was a British writer and poet, best known for her abridgements of J. M. Barrie's Peter Pan books. She published under the names May Byron, M.C. Gillington and Maurice Clare. Byron specialised in writing biographies of great composers, poets and writers, before going on to rewrite some of J. M. Barrie's works for younger readers, to write poetry, and to write cookbooks.

May Edginton was an English writer who had over 50 popular novels published in London. She also wrote plays, collaborating with Rudolf Besier on two of them. Some of her fiction works were filmed. Her work was translated into several languages, including Hungarian and Chinese.

May Sinclair was the pseudonym of Mary Amelia St. Clair, a popular British writer who wrote about two dozen novels, short stories and poetry. She was an active suffragist, and member of the Woman Writers' Suffrage League. She once dressed up as a demure, rebel Jane Austen for a suffrage fundraising event. Sinclair was also a significant critic in the area of modernist poetry and prose, and she is attributed with first using the term 'stream of consciousness' in a literary context, when reviewing the first volumes of Dorothy Richardson's novel sequence Pilgrimage (1915–1967), in The Egoist, April 1918.

Mazo de la Roche was a Canadian writer who was the author of the Jalna novels, one of the most popular series of books of her time.

Melville Louis Kossuth "Melvil" Dewey was an influential American librarian and educator, inventor of the Dewey Decimal system of library classification, a founder of the Lake Placid Club, and a chief librarian at Columbia University. He was also a founding member of the American Library Association. Although Dewey's contributions to the modern library are widely recognized, his legacy is marred by allegations of sexual harassment, racism, and antisemitism.

Melville Davisson Post was an American writer, born in Harrison County, West Virginia. Although his name is not immediately familiar to those outside of specialist circles, many of his collections are still in print, and many collections of detective fiction include works by him. Post's best-known character is the mystery solving, justice dispensing West Virginian backwoodsman, Uncle Abner. The 22 Uncle Abner tales, written between 1911 and 1928, have been called some of "the finest mysteries ever written".

Mercy Otis Warren was an American activist poet, playwright, and pamphleteer during the American Revolution. During the years before the Revolution, she had published poems and plays that attacked royal authority in Massachusetts and urged colonists to resist British infringements on colonial rights and liberties. She was married to James Warren, who was likewise heavily active in the independence movement.

Meredith Nicholson was a best-selling author from Indiana, United States, a politician, and a diplomat.

Metta Victoria Fuller Victor, who used the pen name Seeley Regester among others, was an American novelist, credited with authoring of one of the first detective novels in the United States. She wrote more than 100 dime novels, pioneering the field.

Michael Arlen was a British essayist, short story writer, novelist, playwright, and scriptwriter. He had his greatest successes in the 1920s while living and writing in England. Arlen is most famous for his satirical romances set in English smart society, but he also wrote gothic horror and psychological thrillers, for instance "The Gentleman from America", which was filmed in 1956 as a television episode for Alfred Hitchcock's TV series Alfred Hitchcock Presents. Near the end of his life, Arlen mainly occupied himself with political writing. Arlen's vivid but colloquial style "with unusual inversions and inflections with a heightened exotic pitch" came to be known as 'Arlenesque'.