Queen Consort of the notorious womanizer King Charles II (1638 - 1705) was a Portuguese Infanta. Infanta Catarina of Portugal (or of Braganza) was born in Vila Vicosa as the second surviving daughter of John IV of Portugal (at the time Duke of Braganza) and his wife, Louise of Guzman (Medina-Sidonia). Through her mother, she was a 2nd great granddaughter of Saint Francis Borgia. Although convent raised, Catherine's upbringing and education were closely supervised by her mother. Following the restoration of a Portuguese Royal House, and her father's accession to the throne on 1 December 1640, she was variously proposed as a bride for John of Austria, Francois de Vendome, duc de Beaufort, Louis XIV and Charles II. She was seen as a useful conduit for contracting an alliance between Portugal and England, after the Treaty of the Pyrenees in 1659 in which Portugal was arguably abandoned by France. Upon Charles' restoration to the English throne in 1660, Catherine's mother reopened negotiations with his counselors, and a marriage treaty was signed 23 June 1661. She was married by proxy in Lisbon on 23 April 1662. After her arrival at Portsmouth on 14 May 1662, the couple were married in two more ceremonies, a Catholic one conducted in secret, followed by a public Anglican service on 21 May. Her large dowry brought the port cities of Tangier and Bombay to British control. At the time, she was not a particularly popular choice of queen, being a Roman Catholic, and her religion prevented her from ever being crowned, since Roman Catholics were forbidden to take part in Anglican services. She initially faced hardships due to the language barrier, the king's infidelities and the political conflicts between Roman Catholics and Anglicans. Over time, her quiet decorum, loyalty and genuine affection for Charles changed the public's perception of her.

Catherine became pregnant and miscarried at least twice, and during a severe illness in 1663 she thought for a time she had given birth. Charles comforted her by telling her she had indeed given birth to two sons and a daughter. Her position was a difficult one, as Charles continued to have children by his many mistresses, but he insisted that she be treated with respect, and sided with her over his mistresses in those cases where he felt she was not receiving the respect she was due. Throughout his reign, he firmly dismissed the idea of divorcing Catherine, even when Parliament exerted pressure on him to beget or declare a Protestant successor. Though known to keep her faith a private matter, her religion and proximity to the king made her the target of anti-Catholic sentiment. In 1678, the murder of Sir Edmund Godfrey was ascribed to several of her servants. In November of the same year she was accused by Titus Oates, an instigator of the "Popish Plot", of being part of a conspiracy to poison the king, even though Charles himself disbelieved the entirety of the plot. Although both the evidence in her case and the Popish Plot were later discovered to be fabrications, the House of Commons voted unsuccessfully for an address calling for the Queen and her household to be banished from Whitehall. In 1679 she was defended against the allegations by the king himself.