Pedro Gutiérrez de Valdivia or Valdiva (Spanish pronunciation: [ˈpeðɾo ðe βalˈdiβja]; April 17, 1497 – December 25, 1553) was a Spanish conquistador and the first Governor of Colonial Chile. After having served with the Spanish army in Italy and Flanders, he was sent to South America in 1535, where he served as a soldier under the Pizarro brothers in Peru, gradually rising in power.

In 1540, Valdivia led an expedition of 150 Spaniards and 1,000 Peruvian Indians into Chile, where he defeated a large force of indigenous warriors and founded Santiago in 1541. He extended Spanish rule south to the Biobío River in 1546, fought again in Peru (1546–1548), and returned to Chile as Royal Governor in 1549. In 1550, he expanded Spanish rule further south into Araucanía, where he founded the city of Concepción and the eponymous city of Valdivia. He was captured and killed by Mapuche Indians during the Arauco War in 1553.

Pedro de Valdivia is believed to have been born in Villanueva de la Serena (some say Castuera) in Extremadura, Spain, around 1500 (some sources put his date of birth as early as 1497 or as late as 1505) to an impoverished hidalgo family. In 1520 a civil war broke out in Castile, the Revolt of the Comuneros, and Valdivia joined the royalist army of King Charles I. He later fought in Flanders in 1521 and Italy between 1522 and 1527, participating in the Battle of Pavia as part of the troops of the Marquis of Pescara. In May 1527, Valdivia was involved in the sack of Rome as a member of Charles I's mutinous mercenary army.

Valdivia sailed with a Spanish military force to South America in 1535. He first arrived in present-day Venezuela and stayed there for one year. During his time there, he likely fought against the Carib Indians, who were known for being warlike.

Valdivia traveled south to Peru in 1537. During this time, there was a civil war between the Spanish colonists in Peru, with one faction led by Francisco Pizarro and the other faction led by Diego de Almagro. Valdivia sided with Pizarro's faction and helped them defeat Almagro at the Battle of Las Salinas in 1538. Afterwards, Valdivia accompanied Hernando and Gonzalo Pizarro on an expedition to conquer High Peru (later known as Bolivia). As a reward for helping the Pizarro brothers, Valdivia was given an encomienda property with a silver mine in Potosí. This large silver mine that Valdivia owned made him a very rich man.

Valdivia had married Marina Ortíz de Gaete in Spain. In Peru he became attached to Inés de Suárez, a Spanish widow who accompanied him to Chile as his mistress.

After the failure of the expedition of Diego de Almagro in 1536, the lands to the south of Peru (then known as Nueva Toledo, extending from the 14° — close to modern day Pisco, Peru — to the 25° latitude — close to Taltal, Chile) had remained unexplored. Valdivia asked Governor Francisco Pizarro for permission to conquer and govern that territory. He got his permission but was appointed as Lieutenant Governor, rather than Governor as he had wanted.

The expedition was fraught with problems from the beginning. Valdivia had to sell the lands and the mine that had been assigned to him in order to finance the expedition. A shortage of soldiers and adventurers was also problematic; the men were not interested in conquering what they believed were extremely poor lands. While Valdivia was preparing the expedition, Pedro Sánchez de la Hoz arrived from Spain with a royal grant for the same territory. To avoid difficulties, Pizarro advised the two competitors to join their interests, and on December 28, 1539, they signed a contract of partnership.