Born Wilhelm Apollinaris de Kostrowitzky and raised speaking French, among other languages, he emigrated to France and adopted the name Guillaume Apollinaire. His mother, born Angelica Kostrowicka, was a Polish noblewoman born near Navahrudak (now in Belarus). Apollinaire's father is unknown but may have been Francesco Flugi d'Aspermont, a Swiss Italian aristocrat who disappeared early from Apollinaire's life. Apollinaire was partly educated in Monaco.

Apollinaire was one of the most popular members of the artistic community of Montparnasse in Paris. His friends and collaborators in that period included Pablo Picasso, Gertrude Stein, Max Jacob, André Salmon, Marie Laurencin, André Breton, André Derain, Faik Konica, Blaise Cendrars, Pierre Reverdy, Alexandra Exter, Jean Cocteau, Erik Satie, Ossip Zadkine, Marc Chagall, and Marcel Duchamp. In 1911, he joined the Puteaux Group, a branch of the cubist movement.

On 7 September 1911, police arrested and jailed him on suspicion of stealing the Mona Lisa, but released him a week later. Apollinaire then implicated his friend Pablo Picasso, who was also brought in for questioning in the art theft, but he was also exonerated. He once called for the Louvre to be burnt down.

He fought in World War I and, in 1916, received a serious shrapnel wound to the temple. He wrote Les Mamelles de Tirésias while recovering from this wound. During this period he coined the word surrealism in the program notes for Jean Cocteau and Erik Satie's ballet Parade, first performed on 18 May 1917. He also published an artistic manifesto, L'Esprit nouveau et les poètes. Apollinaire's status as a literary critic is most famous and influential in his recognition of the Marquis de Sade, whose works were for a long time obscure, yet arising in popularity as an influence upon the Dada and Surrealist art movements going on in Montparnasse at the beginning of the twentieth century as, "The freest spirit that ever existed."

The war-weakened Apollinaire died of influenza during the Spanish Flu pandemic of 1918. He was interred in the Père Lachaise Cemetery, Paris.

Apollinaire's first collection of poetry was L'enchanteur pourrissant (1909), but Alcools (1913) established his reputation. The poems, influenced in part by the Symbolist, juxtapose the old and the new, combining traditional poetic forms with modern imagery. In 1913, Apollinaire published the essay Les Peintres cubistes on the cubist painters, a movement which he helped to define. He also coined the term orphism to describe a tendency towards absolute abstraction in the paintings of Robert Delaunay and others.

In 1907, Apollinaire wrote the well-known erotic novel, The Eleven Thousand Rods (Les Onze Mille Verges). Officially banned in France until 1970, various printings of it circulated widely for many years. Apollinaire never publicly acknowledged authorship of the novel. Another erotic novel attributed to him was The Exploits of a Young Don Juan (Les exploits d'un jeune Don Juan), in which the 15-year-old hero fathers three children with various members of his entourage, including his aunt. The book was made into a movie in 1987.

Shortly after his death, Calligrammes, a collection of his concrete poetry (poetry in which typography and layout adds to the overall effect), and more orthodox, though still modernist poems informed by Apollinaire's experiences in the First World War and in which he often used the technique of automatic writing, was published.

In his youth Apollinaire lived for a short while in Belgium, mastering the Walloon dialect sufficiently to write poetry through that medium, some of which has survived.

Poetry:

• Le bestiaire ou le cortège d’Orphée, 1911
• Alcools, 1913
• Vitam impendere amori', 1917
• Calligrammes, poèmes de la paix et de la guerre 1913-1916, 1918 (published shortly after Apollinaire's death)
• Il y a..., 1925
• Julie ou la rose, 1927
• Ombre de mon amour, poems addressed to Louise de Coligny-Châtillon, 1947
• Poèmes secrets à Madeleine, pirated edition, 1949
• Le Guetteur mélancolique, previously unpublished works, 1952
• Poèmes à Lou, 1955
• Soldes, previously unpublished works, 1985
• Et moi aussi je suis peintre, album of drawings for Calligrammes, from a private collection, published 2006

Prose:

• Mirely ou le Petit Trou pas cher, 1900
• "Que faire?",
• Les Onze Mille Verges ou les amours d'un hospodar, 1907
• L'enchanteur pourrissant, 1909
• L'Hérèsiarque et Cie (short story collection), 1910
• Les exploits d’un jeune Don Juan, 1911
• La Rome des Borgia, 1914
• La Fin de Babylone - L'Histoire romanesque 1/3, 1914
• Les Trois Don Juan - L'Histoire romanesque 2/3, 1915
• Le poète assassiné, 1916
• La femme assise, 1920
• Les Épingles (short story collection), 1928

Plays:

• Les Mamelles de Tirésias, play, 1917
• La Bréhatine, screenplay (collaboration with André Billy), 1917
• Couleurs du temps, 1918
• Casanova, published 1952

Articles:

• Le Théâtre Italien, illustrated encyclopedia, 1910
• Pages d'histoire, chronique des grands siècles de France, chronicles, 1912
• Méditations esthétiques. Les peintres cubistes, 1913
• La Peinture moderne, 1913
• L'Antitradition futuriste, manifeste synthèse, 1913
• Case d'Armons, 1915
• L'esprit nouveau et les poètes, 1918
• Le Flâneur des Deux Rives, chronicles, 1918