The eponymous hero is born as a male nobleman in England during the reign of Elizabeth I. He undergoes a mysterious change of sex at the age of about 30 and lives on for more than 300 years into modern times without aging perceptibly.
As a teenaged boy, the handsome Orlando serves as a page at the Elizabethan court and becomes "favorite" of the elderly queen. After her death he falls deeply in love with Sasha, an elusive and somewhat feral princess in the entourage of the Russian embassy. This episode, of love and ice skating against the background of the celebrated Frost Fair held on the frozen Thames River during the Great Frost of 1608, when "birds froze in mid air and fell like stones to the ground", inspired some of Virginia Woolf's most bravura writing:
Great statesmen, in their beards and ruffs, despatched affairs of state under the crimson awning of the Royal Pagoda ... Frozen roses fell in showers when the Queen and her ladies walked abroad ... Near London Bridge, where the river had frozen to a depth of some twenty fathoms, a wrecked wherry boat was plainly visible, lying on the bed of the river where it had sunk last autumn, overladen with apples. The old bumboat woman, who was carrying her fruit to market on the Surrey side, sat there in her plaids and farthingales with her lap full of apples, for all the world as if she were about to serve a customer, though a certain blueness about the lips hinted the truth.
The melting of the ice coincides with Sasha's unfaithfulness and sudden departure for Russia. The desolate Orlando returns to writing The Oak Tree, a long poem started and abandoned in his youth. He meet and hospitably entertains an invidious poetaster, Nicholas Greene, who proceeds to find fault with Orlando's writing. Later Orlando feels betrayed on learning that he has been lampooned in one of Greene's subsequent works. A period of contemplating love and life leads Orlando to appreciate the value of his ancestral stately home, which he proceeds to furnish lavishly. There he plays host to the populace.
Ennui sets in and the harassment of a persistent suitor, the tall and somewhat androgynous Archduchess Harriet, leads Orlando to look for a way to flee the country. He is appointed by King Charles II as ambassador to Constantinople. Orlando performs his duties well, until a night of civil unrest and murderous riots. He falls asleep for a period of days, resistant to all efforts to rouse him. Upon awakening he finds that he has metamorphosed into a woman – the same person, with the same personality and intellect, but in a woman's body. Although the narrator of the novel professes to be disturbed and befuddled by Orlando's change, the fictional Orlando complacently accepts the change. From here on, Orlando's amorous inclinations change frequently although she stays biologically female.
The now Lady Orlando covertly escapes Constantinople in the company of a Gypsy clan. She adopts their way of life until its essential conflict with her upbringing leads her to head home. Only on the ship back to England, with her constraining female clothes and an incident in which a flash of her ankle nearly results in a sailor's falling to his death, does she realize the magnitude of becoming a woman. She concludes it has an overall advantage, declaring "Praise God I'm a woman!" Back in England, Orlando is hounded again by the archduchess, who now reveals herself to be a man, the Archduke Harry. Orlando evades his marriage proposals. She goes on to live switching between gender roles, dressing alternately as both man and woman.
Orlando soon becomes caught up in the life of the 18th and 19th centuries, holding court with the great poets (notably Alexander Pope). Critic Nick Greene, apparently also timeless, reappears and promotes Orlando's writing, promising to help her publish The Oak Tree.
Orlando wins a lawsuit over her property and marries a sea captain, Marmaduke Bonthrop Shelmerdine. Like Orlando, he is gender non-conforming, and Orlando attributes the success of their marriage to this similarity. In 1928, she publishes The Oak Tree, centuries after starting it, and wins a prize. The novel ends as Orlando's husband's ship returns and, in the aftermath of her success, she rushes to greet him.