Ady was born in Érmindszent, Szilágy County (part of Austria-Hungary at the time; now a village in Satu Mare County, Romania, called Adyfalva in Hungarian and Ady Endre in Romanian). He belonged to an impoverished Calvinist noble family. Endre was the second of three children. The eldest, a girl named Ilona, died at an early age. The author and poet Mariska Ady (1888 - 1977) was a niece of Endre Ady.

Between 1892-1896, Ady attended the Calvinist College in Zalău. On 22 March 1896, he published his first poem in the Zalău newspaper Szilágy.

He later studied law at the Reformed College in Debrecen. After finishing his studies, he became a Journalist. He published his first poems in a volume called Versek (Poems) in 1899. He soon grew tired of Debrecen (the town later became a symbol of backwardness in his poetry) and moved to Nagyvárad (today Oradea, Romania), a city with a rich cultural life. In articles written in 1902 for the local newspaper Nagyváradi Napló, Ady paid close attention to the social features of his time. "Wesselényi and a poor peasant! Perhaps unwittingly, master Fadrusz has carved a satire", he wrote, referring to the opening of the Wesselényi Monument.

Working as a Journalist and spending time with like-minded people broadened his horizons. He published a new collection of poems in 1903, but remained relatively unknown. The turning point came in August 1903 when he met Adél Brüll (Mrs Diósy), a rich married Jewish woman who was living in Paris but was visiting her home in Nagyvárad. Léda (as he called her in his poems) became his muse; his love for her and his visit to Paris, where he followed her, helped him to develop his talent. He visited Paris seven times between 1904 and 1911. When he returned after his first visit (which lasted for a year), he moved to Budapest and began work for the newspaper Budapesti Napló (Budapest Journal), where he published more than 500 articles and many poems.

In 1906 Ady decided to leave the country and went to Paris again. In 1907, he had to leave his job at Budapesti Napló.

In 1908, the first issue of a new periodical called Nyugat (The West) published a poem and an essay by Ady. He worked for this periodical for the rest of his life; from 1912 he was one of the editors. Also in 1908 in Nagyvárad, he was one of the founders of a literary circle called A Holnap (Tomorrow). The circle published an anthology of poems of Ady and others including Mihály Babits, Gyula Juhász and Béla Balázs. The poems of this anthology met with disapproval and incomprehension. Many people attacked the anthology for containing erotic poems. In addition, Ady was criticized for his unpatriotic feelings in a poem in which he emphasized the contrast between the rich cultural life he longed for and the cruel realities of the Hungarian peasant world.

From 1909 he often needed treatment in sanatoria for his health, which was undermined by syphilis. The political situation became critical: the workers were protesting against the government, and Ady saw a revolution approaching. His personal life was also in crisis; his affair with Léda became more and more of a burden for him. As Ady become a prominent poet, Léda lost her leading role in the relationship. He broke up with her in April 1912.

In 1914 he met the 20-year-old Berta Boncza, with whom he had been corresponding since 1911. In 1915 they married without her father's permission. In his poems he called her Csinszka.

After the assassination of Archduke Franz Ferdinand in 1914, Ady saw that war was approaching. Everyone he knew was enthusiastic about the war, and he was left alone with his fears and worries about the Future. He published his last book of poetry in 1918. He was terminally ill when he wrote his last poem, "Üdvözlet a győzőnek" (Greetings to the victorious). Syphilis had weakened his aorta, so that he might die at any moment from a massive haemorrhage. He was elected as President of the Vörösmarty Academy, an organization of modern Writers, but could not deliver his opening speech; he died in Budapest on 27 January 1919.

His first two books of poetry did not show anything new; he was still under the influence of 19th-century poets such as Petőfi or János Vajda. The first elements of his own style appeared not in his poems but in his essays and other writings.