Cavafy was born in 1863 in Alexandria, Egypt, to Greek parents, and was baptized into the Greek Orthodox Church. His father was a prosperous importer-exporter who had lived in England in earlier years and acquired British nationality. After his father died in 1870, Cavafy and his family settled for a while in Liverpool in England. In 1876, his family faced financial problems following the crash, so, by 1877, they had to move back to Alexandria. In 1882, disturbances in Alexandria caused the family to move again, though temporarily, to Constantinople. This was the year when a revolt broke out in Alexandria against the Anglo-French control of Egypt, thus precipitating the 1882 Anglo-Egyptian War. Alexandria was bombarded by a British fleet and the family apartment at Ramli was burned.

In 1885, Cavafy returned to Alexandria, where he lived for the rest of his life. His first work was as a journalist; then he took a position with the British-run Egyptian Ministry of Public Works for thirty years. (Egypt was a British protectorate until 1926.) He published his poetry from 1891 to 1904 in the form of broadsheets, and only for his close friends. Any acclaim he was to receive came mainly from within the Greek community of Alexandria. Eventually, in 1903, he was introduced to mainland-Greek literary circles through a favourable review by Xenopoulos. He received little recognition because his style differed markedly from the then-mainstream Greek poetry. It was only 20 years later, after the Greek defeat in the Greco-Turkish War (1919-1922), that a new generation of almost nihilist poets (e.g. Karyotakis) would find inspiration in Cavafy's work.

A biographical note written by Cavafy reads as follows:

"I am from Constantinople by descent, but I was born in Alexandria—at a house on Seriph Street; I left very young, and spent much of my childhood in England. Subsequently I visited this country as an adult, but for a short period of time. I have also lived in France. During my adolescence I lived over two years in Constantinople. It has been many years since I last visited Greece. My last employment was as a clerk at a government office under the Ministry of Public Works of Egypt. I know English, French, and a little Italian."

It is generally accepted that Cavafy was homosexual and overtly gay themes appear in a large number of his poems.

He died of cancer of the larynx on April 29, 1933, his 70th birthday. Since his death, Cavafy's reputation has grown. He is now considered one of the finest European and modern Greek poets. His poetry is taught at schools in mainland Greece and Cyprus, and across universities around the world. E.M. Forster knew him personally and wrote a memoir of him, contained in his book Alexandria.

Cavafy was instrumental in the revival and recognition of Greek poetry both at home and abroad. His poems are, typically, concise but intimate evocations of real or literary figures and milieux that have played roles in Greek culture. Uncertainty about the future, sensual pleasures, the moral character and psychology of individuals, homosexuality, and a fatalistic existential nostalgia are some of the defining themes. Besides his subjects, unconventional for the time, his poems also exhibit a skilled and versatile craftsmanship, which is almost completely lost in translation. Cavafy was a perfectionist, obsessively refining every single line of his poetry. His mature style was a free iambic form, free in the sense that verses rarely rhyme and are usually from 10 to 17 syllables. In his poems, the presence of rhyme usually implies irony. Cavafy drew his themes from personal experience, along with a deep and wide knowledge of history, especially of the Hellenistic era. Many of his poems are pseudo-historical, or seemingly historical, or accurately, but quirkily, historical.

One of Cavafy's most important works is his 1904 poem "Waiting for the Barbarians". This work, in the person of a disingenuous Byzantine narrator, cynically explores the view that cultivating fear of an invisible external enemy usually serves internal purposes. Parallels have been drawn between the poem's message and the 21st-century war on terror. In 1911, Cavafy wrote Ithaca, inspired by the Homeric return journey of Odysseus to his home island, as depicted in the Odyssey. The poem's theme is that enjoyment of the journey of life, and the increasing maturity of the soul as that journey continues, are all the traveler can ask.

Ithaca

Cavafy divides his own work into three categories:

Historical poems

These poems are mainly inspired by the Hellenistic era with Alexandria at primary focus. Other poems originate from Helleno-romaic antiquity and the Byzantine era. Mythological references are also present. The periods chosen are mostly of decline and decadence (eg Trojans); his heroes facing the final end.

Sensual poems

The sensual poems are filled with lyricism and emotion; inspired by recollection and remembrance. The past and former actions, sometimes along with the vision for the future underlie the muse of Cavafy in writing these poems.

Philosophical poems

Also called instructive poems they are divided into poems with consultations to poets and poems that deal with other situations such as closure (for example, "The walls"), debt (for example, "Thermopylae"), and human dignity (for example, "The God Abandons Antony").