Percy Bysshe Shelley (1792–1822) first published "Ozymandias" in the 11 January 1818 issue of The Examiner and included it in his book-length collection of poems Rosalind and Helen, A Modern Eclogue; with Other Poems in 1819.

The title of the poem "Ozymandias" is the Greek name for the Egyptian pharaoh Ramesses (sometimes spelled Ramses) II, also known as Ramesses the Great (c. 1303 BCE – 1213 BCE). He was the third pharaoh of the Egyptian Nineteenth Dynasty and reigned from 1279 to 1213 BCE. He was the most important ruler of the period known as the New Kingdom and notable for his many military victories, his building numerous extravagant monuments and temples, and his bringing Egypt into a period of great prosperity and power. Shelley would have been familiar with him under the name Ozymandias from The Histories of Herodotus (c. 484 – c. 425 BCE), an ancient Greek historian who visited Egypt and told of his travels there and the various historical accounts given by Egyptians as he toured notable monuments. Herodotus was a standard school text in Shelley's period, and Shelley would have read it in the original Greek, which is why he uses the Greek version of the pharaoh's name. The direct inspiration for the poem was the work of another Greek historian, Diodorus Siculus (fl. 1st century BCE) who describes a monumental statue with the inscription in his Bibliotheca historica:

King of Kings am I, Ozymandias. If anyone would know how great I am and where I lie, let him surpass one of my works.

In the late eighteenth century, Napoleon invaded Egypt, leading to a dramatic rise in interest in Egyptian archaeology among Europeans. The British Museum had acquired a large statue of Ozymandias shortly before the poem was written, and it was in the process of being shipped to England when the poem was published. Thus the poem is not just historical but reflects what were current events.

"Ozymandias" is written in the form of a sonnet, a fourteen-line poem using regular meter and end-rhymes. The rhythmical pattern of the poem is iambic pentameter, meaning that each line consists of five iambic feet, with an iambic foot being an unstressed followed by a stressed syllable. The rhyme scheme is somewhat irregular. Structurally, the poem has the surprising twist in the final two lines normally associated with the Shakespearean sonnet, but the rhyme scheme is closer to the Italian form. The rhyme scheme can be represented as abab acdc ede fef.

Although the work uses occasional forms of specific poetic diction, such as the inverted syntax of the line "its sculptor well those passions read," the vocabulary and diction tend to be simple and direct. The language generally eschews metaphor but does use devices such as alliteration, as exemplified in the phrases "cold command" and "boundless and bare."

Little detail is given about the first-person narrator of the poem. The narrator encounters a traveler who visited Egypt, and the body of the poem is a quotation, consisting of what the traveler told the narrator. This sort of framing was typical of fiction and exotic tales in Shelley's period, with the framing used to give stories verisimilitude. The lack of information about narrator and traveler keeps the focus of the poem centered on the statue and the way modern people might encounter the past rather than the specific experiences of a narrator.

Generically, this is often described as a "monument" poem, a genre originating in Horace's Odes III: XXX (23 BCE), in which the poet states of his work:

I have built a monument more lasting than bronze,
higher than the Pyramids’ regal structures,
that no consuming rain, nor wild north wind
can destroy . . .

Also using the sonnet form is another monument poem, William Shakespeare's Sonnet 59, which begins:

Not marble nor the gilded monuments
Of princes shall outlive this powerful rhyme . . .

In Shelley's poem, readers encounter a similar vision of a colossal monument of the greatest of the Egyptian pharaohs which is crumbling into dust. The inscription, however, has outlasted the statue, and it is implied that so, too, will Shelley's poem, which people are reading in 1818—long after the fall of Egypt, successively to Alexander the Great, the Roman Empire, and recently (to Shelley's readers) Napoleon. This theme expresses Shelley's own conception of the importance of poetry and poets, whom he views as more powerful than rulers or military leaders because of the way they shape the thought and cultural trajectory of people. As an atheist, Shelley saw poetry as especially important to the human spirit, replacing the obsolete superstitions of religion. Thus the statue of Ozymandias, who built great Egyptian temples, passes away into history, but the poem of the atheist Shelley remains in its place.

Another major theme of the poem is the nature of power. Shelley was an avid republican, opposed to monarchy and tyranny in all forms and enthusiastically supporting democratic revolutions. Ozymandias is portrayed as arrogant and sneering, a cruel tyrant against whom the sculptor was subtly rebelling by emphasizing the harshness of his features. This also reflects Shelley's view of artists (including poets) as speaking truth to power and standing up against tyranny. The fallen statue suggests that tyrants shall all eventually fall or be overthrown and their memories fade away.

The major theme of the poem is that often represented by the Latin phrase "sic transit gloria mundi" (thus passes the glory of the world). The ephemeral nature of even this great statue is introduced at the beginning of the traveler's description: "on the sand, / Half sunk a shattered visage lies." The poem concludes with a poignant and striking image of the fallen statue, emphasizing how it is crumbling to dust:

Nothing beside remains. Round the decay
Of that colossal Wreck, boundless and bare
The lone and level sands stretch far away.

The Italian sonnet presents the poet with the challenge of using an utterly familiar form in an innovative or provocative way. The chief variables within this form involve rhyme scheme. The traditional Italian sonnet features an abba, abba, cde, cde rhyme scheme, each letter representing a different end rhyme that is repeated in pattern.

In “Ozymandias,” Shelley chooses to forgo the conventional scheme and employs a more eccentric abab, acdc, ece, fef pattern that creates the immediate effect of a woven tapestry of sound and rhythm that helps to underscore the poem’s essential irony. As the reader’s expectations are unmet, the very syntax forced by the unusual rhyme of the poem creates tension that matches that of the theme.

Critics have long noted the “Chinese box” frame in which the story of Ozymandias has come to the poet and thus, indirectly, to the reader. Each line of the poem, from first to last, reveals successively one more layer of the narrative’s essential irony.

One learns first something of the poet’s conversation with the mysterious traveler “from an antique land.” The poet, in turn, reports but one tidbit of that conversation, “Who said—,” in the very words of the traveler. Laboriously, the speaker then moves through each wave of recognition and interpretation of what he has encountered, climaxing with the presentation of Ozymandias’s inscription.

Shelley’s sonnet is remarkable for its spare and stark imagery. The poet is determined to re-create the barren desert landscape, the poetic counterpoint to the morbid and deserved fate of Ozymandias, the pompous fool. To do so requires that he carefully circumscribe his choice of descriptors to connote neither grandeur nor panoramic vista, but rather singular loneliness and constrained, fragmented solitude. Hence such modifiers as “trunkless,” “Half-sunk,” “shattered,” “decay,” and “wreck” serve his purpose well.

Consequently, the compression of the sonnet form, the unconventional rhyme scheme, the point of view chosen for reader entry, and the carefully wrought diction of the poem achieve the effect the poet was seeking. Amid vast stretches of unbroken sameness, the traveler—followed by the poet, then the reader—comes upon a bleak personage whose severed limbs and head first shock and dismay, then elicit reluctant mockery for the egotism of its subject.