Charles II (Charles Stuart; 29 May 1630 – 6 February 1685) was the King of England, Scotland, and Ireland.

According to royalists, Charles II became king when his father Charles I was executed at Whitehall on 30 January 1649, the climax of the English Civil War. The English Parliament did not proclaim Charles II king at this time, passing a statute making it unlawful, and England entered the period known to history as the English Interregnum. The Parliament of Scotland, on the other hand, proclaimed Charles II King of Scots on 5 February 1649 in Edinburgh. He was crowned King of Scots at Scone on 1 January 1651. Following his defeat at the Battle of Worcester on 3 September 1651, Charles fled to the continent and spent the next nine years in exile in France, the United Provinces and the Spanish Netherlands.

After the Protectorate collapsed under Richard Cromwell in 1659, General George Monck invited Charles to return and assume the thrones in what became known as the Restoration. Charles II arrived on English soil on 25 May 1660 and entered London on his thirtieth birthday, 29 May 1660. Charles was crowned King of England and Ireland at Westminster Abbey on 23 April 1661.

Charles's English parliament enacted harsh anti-Puritan 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 himself favoured a policy of religious toleration. The major foreign policy issue of Charles's early reign was the Second Anglo-Dutch War. In 1670, Charles entered into the secret treaty of Dover, an alliance with Louis XIV under the terms of which Louis agreed to aide Charles in the Third Anglo-Dutch War and pay Charles a pension, and Charles promised to convert to Roman 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 (the future James II) was a Roman Catholic. This crisis saw the birth of the pro-exclusion Whig and anti-exclusion Tory parties. Charles sided with the Tories, and, following the discovery of the Rye House Plot to murder Charles and James in 1683, some Whig leaders were killed or forced into exile. Charles dissolved the English Parliament in 1679, and ruled alone until his death on 6 February 1685. Charles converted to Roman Catholicism on his deathbed.

He was popularly known as the Merrie Monarch, in reference to both the liveliness and hedonism of his court and the general relief at the return to normality after over a decade of rule by Oliver Cromwell and the Puritans. Charles's wife, Catherine of Braganza, was barren, but Charles acknowledged at least 12 illegitimate children by various mistresses.