Life Is a Dream (Spanish: La vida es sueño [la ˈβiða es ˈsweɲo]) is a Spanish-language play by Pedro Calderón de la Barca. First published in 1636, in two different editions, the first in Madrid and a second one in Zaragoza. Don W. Cruickshank and a number of other critics believe that the play can be dated around 1630, thus making Calderón's most famous work a rather early composition. It is a philosophical allegory regarding the human situation and the mystery of life. The play has been described as "the supreme example of Spanish Golden Age drama". The story focuses on the fictional Segismundo, Prince of Poland, who has been imprisoned in a tower by his father, King Basilio, following a dire prophecy that the prince would bring disaster to the country and death to the King. Basilio briefly frees Segismundo, but when the prince goes on a rampage, the king imprisons him again, persuading him that it was all a dream.

The play's central themes are the conflict between free will and fate, as well as restoring one's honor. It remains one of Calderón's best-known and most studied works, and was listed as one of the 40 greatest plays of all time in The Independent. Other themes include dreams vs. reality and the conflict between father and son. The play has been adapted for other stage works, in film and as a novel.

Catholic Spain was the most powerful European nation by the 16th century. The Spanish Armada was defeated by England in 1588, however, while Spain was trying to defend the northern coast of Africa from the expansion of the Turkish Ottoman Empire, and the gold and silver that Spain took from its possessions in the New World were not adequate to sustain its subsequent decades of heavy military expenses. Spain's power was rapidly waning by the time Calderón wrote Life Is a Dream.

The age of Calderón was also marked by deep religious conviction in Spain. The Catholic church had fostered Spanish pride and identity, to the extent that "speaking Christian" became, and remains, synonymous with speaking Spanish.

Another current that permeated Spanish thinking was the departure from the idea that royal power resided in God's will, as noted in Machiavelli's The Prince (1532). Francisco Suárez's treatise On the Defense of Faith (De defensio fidei, 1613) stated that political power resided in the people and rejected the divine rights of kings, and Juan Mariana's On Kings and Kingship (1599) went even further by stating that the people had the right to murder despotic kings.^{[page needed]}

Amidst these developments during the 16th and 17th centuries, Spain experienced a cultural blossoming referred to as the Spanish Golden Age. It saw the birth of notable works of art: Don Quixote, by Miguel de Cervantes (1605), played with the vague line between reality and perception. Lope de Vega, in his play Fuente Ovejuna (1619), talks about a village that rebels against authority.

After being abandoned by their horses, Rosaura, who is dressed as a man, and Clarín walk through the mountains of Poland without food or anywhere to go for the night. They arrive at a tower, where they find Segismundo imprisoned, bound in chains. He tells them that his only crime was being born. Clotaldo, Segismundo's old warden and tutor, arrives and orders his guards to disarm and kill the intruders, but he recognizes Rosaura's sword as his own that he had left behind in Muscovy (for a favor that he owed) years ago for his child to bear. Suspecting that Rosaura is his child (he thinks she is male), he takes Rosaura and Clarín with him to court.

At the palace, Astolfo (Duke of Muscovy) discusses with his cousin, Princess Estrella (Segismundo's cousin), that as they are the nephew and niece of King Basilio of Poland, they would be his successors if they married each other. Estrella is troubled by the locket that Astolfo wears, with another woman's portrait. Basilio reveals to them that he imprisoned his infant son, Segismundo, due to a prophecy by an oracle that the prince would bring disgrace to Poland and would kill his father, but he wants to grant his son a chance to prove the oracle wrong. If he finds him evil and unworthy, he will send him back to his cell, making way for Astolfo and Estrella to become the new king and queen. Clotaldo enters with Rosaura, telling Basilio that the intruders know about Segismundo. He begs for the king's pardon, as he knows he should have killed them. The king says he should not worry, for his secret has already been revealed. Rosaura tells Clotaldo that she wants revenge against Astolfo, but she won't say why. Clotaldo is reluctant to reveal that he thinks he is Rosaura's father.