The Royal Declaration of Indulgence was Charles II of England's attempt to extend religious liberty to Protestant nonconformists and Roman Catholics in his realms, by suspending the execution of the Penal Laws that punished recusants from the Church of England. Charles issued the Declaration on 15 March 1672.

It was highly controversial and Sir Orlando Bridgeman, son of a bishop, resigned as Lord Keeper of the Great Seal, because he refused to apply the Great Seal to it, regarding it as too generous to Catholics.

In 1673 the Cavalier Parliament compelled Charles to withdraw the declaration and implement, in its place, the first of the Test Acts (1673), which required anyone entering public service in England to deny the Catholic doctrine of transubstantiation and to take Anglican communion. When Charles II's openly Catholic successor James II attempted to issue a similar Declaration of Indulgence, an order for general religious tolerance, it became one of the grievances that led to the Glorious Revolution which ousted him from the throne.

Charles II (29 May 1630 – 6 February 1685) was King of Scotland from 1649 until 1651, and King of England, Scotland and Ireland from the 1660 Restoration of the monarchy until his death in 1685.

Charles II was the eldest surviving child of Charles I of England, Scotland and Ireland and Henrietta Maria of France. After Charles I's execution at Whitehall on 30 January 1649, at the climax of the English Civil War, the Parliament of Scotland proclaimed Charles II king on 5 February 1649. But England entered the period known as the English Interregnum or the English Commonwealth, and the country was a de facto republic led by Oliver Cromwell. Cromwell defeated Charles II at the Battle of Worcester on 3 September 1651, and Charles fled to mainland Europe. Cromwell became virtual dictator of England, Scotland and Ireland. Charles spent the next nine years in exile in France, the Dutch Republic and the Spanish Netherlands. The political crisis that followed Cromwell's death in 1658 resulted in the restoration of the monarchy, and Charles was invited to return to Britain. On 29 May 1660, his 30th birthday, he was received in London to public acclaim. After 1660, all legal documents stating a regnal year did so as if he had succeeded his father as king in 1649.

Charles's English parliament enacted laws known as the Clarendon Code, designed to shore up the position of the re-established Church of England. Charles acquiesced to the Clarendon Code even though he favoured a policy of religious tolerance. The major foreign policy issue of his early reign was the Second Anglo-Dutch War. In 1670, he entered into the Treaty of Dover, an alliance with his cousin King Louis XIV of France. Louis agreed to aid him in the Third Anglo-Dutch War and pay him a pension, and Charles secretly promised to convert to Catholicism at an unspecified future date. Charles attempted to introduce religious freedom for Catholics and Protestant dissenters with his 1672 Royal Declaration of Indulgence, but the English Parliament forced him to withdraw it. In 1679, Titus Oates's revelations of a supposed Popish Plot sparked the Exclusion Crisis when it was revealed that Charles's brother and heir presumptive, James, Duke of York, had become a Roman Catholic. The crisis saw the birth of the pro-exclusion Whig and anti-exclusion Tory parties. Charles sided with the Tories, and after the discovery of the Rye House Plot to murder Charles and James in 1683, some Whig leaders were executed or forced into exile. Charles dissolved the English Parliament in 1681 and ruled alone until his death in 1685. He was allegedly received into the Catholic Church on his deathbed.

Traditionally considered one of the most popular English kings, Charles is known as the Merry Monarch, a reference to the liveliness and hedonism of his court. He acknowledged at least 12 illegitimate children by various mistresses, but left no legitimate children and was succeeded by his brother, James.