Alexandre Mercereau (22 October 1888 – 1945) was a French symbolist poet and critic associated with Unanimism and the Abbaye de Créteil. He founded the Villa Médicis Libre, which helped impoverished artists and operated as charitable reformatory for delinquent teenagers. Mercereau's work inspired the revolutionary artistic movement of the early 20th century known as Cubism.

Born Alexandre Mercereau de la Chaume, he signed his first texts Eshmer-Valdor, a pseudonym he quickly abandoned. In 1901, at sixteen years of age, Mercereau's first verses were published; poetry and criticism in Oeuvre d'art international. In 1904 he co-founded the magazine La Vie, where he became assistant editor, drama critic, and columnist.

In 1905 he published Les Thuribulums affaissés, a book of verse that attracted much attention. At the same time, he co-founded the Association Ernest-Renan. In 1906 he organized the French section of Salon exhibition and literary review La Toison d'Or.

In 1907 he published Gens de là et d'ailleurs. From 1907 to 1908 he co-founded and participated in the experience of the Abbaye de Créteil, a collective open to artists. Mercereau organized exhibitions of French artists in Moscow, Saint-Petersburg, Kiev, and Odessa. After World War I he published a pamphlet, L'Abbaye et le bolchevisme culturel (published by Eugène Figuière), in which he denounced the attitude of Georges Duhamel and Charles Vildrac. From 1910 he co-directed with Paul Fort the Parisian literary review Vers et Prose. In 1911 he created the literary section of the Salon d'Automne in Paris, called Comité d'initiative théâtrale, consisting of public lectures by emerging authors at the Théâtre de l'Odéon. He subsequently co-founded the Revue indépendante and La Rue, in addition to Vers et Prose.

Mercereau was literary director at Jacques Povolozky & Cie publishing, director of Caméléon, a café littéraire in Montparnasse. In Histoire Contemporaine des Lettres Française de 1885 à 1914 (Eugène Figuière), Ernest Florian-Parmentier writes "... M. Mercereau seems endowed with all the qualities that lead almost inevitably to success.

The Abbaye de Créteil was a phalanstère utopian community founded during the fall of 1906 by Alexandre Mercereau, along with the poets René Arcos, Henri-Martin Barzun, Charles Vildrac, and the artist, theorist Albert Gleizes. The movement drew its inspiration from the Abbaye de Thélème, a fictional creation by Rabelais in his novel Gargantua.

Albert Gleizes met the artists Berthold Mahn, Jacques d'Otémar and Josué Gaboriaud while in Amiens (1904), as well as the printer, Lucien Linard, who would run the printshop at the Abbaye de Créteil. At this time, the art critic Jean Valmy Baysse (and soon historian of the Comédie-Française), in collaboration with Alexandre Mercereau, René Arcos, Charles Vildrac and Georges Duhamel were invited to participate on a new journal, titled La Vie.

Symbolist poet and writer Henri-Martin Barzun joined the group of writers and painters in 1905. Gleizes assisted in the formation of the Association Ernest Renan in December at the Théâtre Pigalle, in an attempt to counter the rise of militarist propaganda. In the process, publications and artwork tended towards a more popular and secular culture. Gleizes was in charge of the literary and artistic developments that organized poetry readings and street theatre.