Pedro Fernandes de Queirós () (1563–1614) was a Portuguese navigator in the service of Spain. He is best known for his involvement with Spanish voyages of discovery in the Pacific Ocean, in particular the 1595–1596 voyage of Álvaro de Mendaña y Neira, and for leading a 1605–1606 expedition that crossed the Pacific in search of Terra Australis. Early life Queirós (or Quirós as he signed) was born in Évora, Portugal in 1563. As the Portuguese and Spanish monarchies had been unified under the king of Spain in 1580 (following the vacancy of the Portuguese throne, which lasted for sixty years, until 1640, when the Portuguese monarchy was restored), Queirós entered Spanish service as a young man and became an experienced seaman and navigator. In April 1595 he joined Álvaro de Mendaña y Neira on his voyage to colonize the Solomon Islands, serving as chief pilot. After Mendaña's death in October 1595, Queirós is credited with taking command and saving the only remaining ship of the expedition, arriving in the Philippines in February 1596. Isabel Barreto, Mendaña's wife, accompanied the expedition and was accused of causing the crew's low morale by her selfishness and strict discipline. The search for Terra Australis Queirós spent eighteen months in the Philippines, but returned to Spain in 1598, via Mexico. Upon his return to Spain, he petitioned King Philip III to support another voyage into the Pacific, hoping to find a large southern continent to claim for Spain. A devout Catholic, Queirós also visited Rome in 1600, where he obtained the support of the Pope, Clement VIII, for further explorations. He greatly impressed the Spanish Ambassador in Rome, the Duke of Sesa, who described him as a “man of good judgement, experienced in his profession, hard working, quiet and disinterested.” While in Rome Queirós also first wrote his Treatise on Navigation as a letter to the king, further reinforcing his reputation as a navigator, and invented two navigational tools. In March 1603 Queirós was finally authorized to return to Peru to organize another expedition, with the intention of finding Terra Australis, the mythical "great south land," and claiming it for Spain and the Church. Queirós was shipwrecked in the West Indies, but made it to Peru by March 1605. Queirós's party of 160 men on three ships, San Pedro y San Pablo (150 tons), San Pedro (120 tons), and the tender (or launch) Los Tres