Was Francis Drake a pirate, and why did Elizabeth I never admit she backed him?

It depends whom you ask. Drake was an English explorer and privateer who made the second circumnavigation of the world, between 1577 and 1580. To the English he was a hero. To the Spanish, whose treasure ships and ports he raided, he was a pirate, known as El Draque, the Dragon. Elizabeth I never signed a formal commission for him, so officially she could say she knew nothing, while quietly collecting her share.

Elizabeth's English adventurers are often called the Elizabethan Sea Dogs. Drake had started out on slaving voyages, but their bitter end turned his life in a different direction, and from then on he dedicated himself to attacking Spanish possessions. His capture of a Spanish silver train at Nombre de Dios in 1573 made him rich and famous. His party buried much of the loot because it was too heavy to carry, and one account suggests this may have given rise to later stories of pirates and buried treasure. When he came home, England had a temporary truce with Philip II of Spain, so the government could not officially acknowledge what he had done.

A great prize came when he captured the treasure ship Nuestra Señora de la Concepción, which carried 80 pounds of gold and about 26 tons of silver. Drake then did something the stereotypical pirate would not: he dined with his prisoners' officers and passengers, and released them with gifts suited to their rank and a letter of safe conduct.

For the round-the-world voyage, the queen kept her distance. Elizabeth likely invested in the 1577 voyage but never issued him a formal commission. She did knight him in 1581, aboard the Golden Hind itself, and in 1588 he was second-in-command of the fleet that repulsed the Spanish Armada.