The theme of usurpation runs throughout Shakespeare's The Tempest and is central to the play.

Interestingly, the term "usurp" itself appears only once in the play: when Prospero accuses Ferdinand of usurping the name of Ferdinand's father, the king of Naples, who Ferdinand assumed had been killed in the shipwreck. Prospero also accuses Ferdinand of being a spy:

PROSPERO: Thou dost here usurp
The name thou ow'st not; and hast put thyself
Upon this island as a spy, to win it
From me, the lord on't. [1.2.540–543]

Nevertheless, the theme of usurpation—political, social, and personal—underscores the action of the play, as well as the related themes of betrayal, natural order, and revenge.

As Prospero explains to his daughter, Miranda, in act 1, scene 2, twelve years ago Prospero was the Duke of Milan, until his brother, Antonio (with the help of the king of Naples) betrayed Prospero, usurped his dukedom, and seized his power.

PROSPERO: The King of Naples, being an enemy
To me inveterate, hearkens my brother's suit;
Which was that he, in lieu o'th’ premises
Of homage and I know not how much tribute,
Should presently extirpate me and mine
Out of the dukedom, and confer fair Milan,
With all the honours, on my brother . . . [1.2.142–148]

Antonio sent Prospero and Miranda into exile on a leaky excuse for a boat, which landed on the shore of their island.

PROSPERO: . . . In few, they hurried us aboard a barque,
Bore us some leagues to sea, where they prepared
A rotten carcass of a butt, not rigged,
Nor tackle, sail, nor mast—the very rats
Instinctively have quit it. . . .

Here in this island we arrived . . . [1.2.169–173, 202]

Good fortune brought the usurpers to the island:

PROSPERO: By accident most strange, bountiful Fortune,
Now my dear lady, hath mine enemies
Brought to this shore . . . [1.2.210–212]

Here, Prospero can use his magic to confuse and confound his enemies and effect his own kind of revenge on them for usurping his dukedom many years ago.

PROSPERO: [to Antonio] For you, most wicked sir, whom to call brother
Would even infect my mouth, I do forgive
Thy rankest fault, all of them, and require
My dukedom of thee, which perforce I know
Thou must restore. [5.1.145–150]

Usurpation is using force to take something that belongs to someone else. This theme emerges in Act I of The Tempest, as we learn that the travelers who were caught in the tempest and spirited to Prospero's island include Antonio, Prospero's brother. Prospero tells Miranda their family history: Prospero wanted time to study books of magic, so he left Antonio in charge of the kingdom. Antonio took advantage of the situation to usurp the throne. After taking over, Antonio had Prospero and the infant Miranda set to drift at sea on a leaky boat. Fortunately, they landed safely on this island. Now Prospero, using magic, has the chance to wreak revenge on his brother for his treachery.

Post-colonial readings also point to Prospero usurping the island that once belonged to Caliban and his mother. Caliban showed Prospero where to find drinking water and arable land, enabling him and his young daughter to survive. However, once Prospero's survival was secure, he usurped the island as his own and enslaved Caliban, calling him a monster.

We learn from these examples the usurpation is not uncommon and that people have to think strategically and not simply trust others if they want to hold on to what they possess.

Usurpation is key to Act I of this play, as Prospero explains to his daughter how they ended up on this enchanted island and in addition how Prospero himself seized power. Clearly in Act I scene 2, Prospero is explaining to Miranda something of her history both for her benefit and the audience's benefit. Prospero begins by telling Miranda how his own brother usurped his role as Duke of Milan and seized power for himself. However much Prospero bemoans how cruel his brother was to seize power from him in such a way, it is clear that he himself does exactly the same thing when he and his daughter reach the island. Note what he reminds Ariel of whilst his daughter sleeps and he talks about Sycorax, his former mistress:

This blue-eyed hag was hither brought with child,

And here was left by th'sailors. Thou, myslave,

As thou report'st thyself, was then her servant;

And for thou wast a spirit too delicate

To act her earthy and abhorred commands...

Sycorax and her son Caliban, oddly mirroring Prospero and Miranda, were likewise sent to the island and exiled there, and Sycorax used her magical arts to seize power and enslave Ariel to her own purposes. It is Prospero who usurped her power when he arrived at the island and freed Ariel, enslaving both Ariel and Caliban into his service. As much as Prospero feels hard done by through his own loss of power, he is quick to usurp the power of another.