Alejo García, also Aleixo Garcia (d. 1525 Paraguay,) was a Portuguese-born explorer and conquistador who explored the Rio de la Plata, Paraguay, and Bolivia in service to Spain.

He was a member of the failed expedition of Juan Diaz de Solís, seeking to find a passage from the Atlantic to the Pacific Ocean. After reaching the mouths of the Uruguay and Parana, it was apparent that the Rio de la Plata was not such a strait. At this point, de Solís was killed - on testimony of his crew - by cannibal Indians (variously identified as the Charrúa or Guaraní) and his lieutenants opted to return to Spain.

On their return, some of their boats were shipwrecked off Santa Catarina in present-day Brazil. Among the survivors was Alejo García, a Portuguese adventurer who had previously made contact with the Guaraní.

He now traveled inland, living among the Guaraní. While there, he heard tales of a "White King" who lived to the west, ruling cities of incomparable riches and splendor.

After eight years, García had gathered enough men and supplies to attempt a voyage to the land of the "White King." Marching towards the west, his company discovered a great waterfall. Credit for the discovery of the Iguazu Falls is usually given to the governor Alvar Núñez Cabeza de Vaca, and historian Efraím Cardozo asserts García crossed the Paraná at the smaller waterfall called Monday.

During 1524 and 1525, the small group recruited an army of about 2,000 local Guaraní soldiers from the vicinity of Asuncion as reinforcement to invade the promising new land. They then entered the Chaco, a rough semi-desert region. García was the first European to cross the Chaco and even managed to penetrate the outer defenses of the Inca Empire on the hills of the Andes, in present-day Bolivia. He was the first European to do so, accomplishing this eight years before Francisco Pizarro.

Garcia looted an impressive booty of silver. When the army of Huayna Cápac arrived to challenge him, García then retreated with the spoils, only to be assassinated by his Indian allies near San Pedro on the Paraguay River.

The Indians, however, spared the life of his son, who was the first Paraguayan mestizo. News of this excursion into Incan territory later distracted Sebastian Cabot from his expedition to the East Indies (which could have resulted in circumnavigation of the globe before Ferdinand Magellan) causing him to imprison or maroon his lieutenants and remain in the Rio de la Plata region for several years.