James VI and I (James Charles Stuart; 19 June 1566 – 27 March 1625) was King of Scotland as James VI from 24 July 1567 and King of England and Ireland as James I from the union of the Scottish and English crowns on 24 March 1603 until his death in 1625. The kingdoms of Scotland and England were individual sovereign states, with their own parliaments, judiciaries, and laws, though both were ruled by James in personal union.

James was the son of Mary, Queen of Scots, and a great-great-grandson of Henry VII, King of England and Lord of Ireland, and thus a potential successor to all three thrones. He succeeded to the Scottish throne at the age of thirteen months, after his mother was compelled to abdicate in his favour. Four different regents governed during his minority, which ended officially in 1578, though he did not gain full control of his government until 1583. In 1603, he succeeded the last Tudor monarch of England and Ireland, Elizabeth I, who died childless. He continued to reign in all three kingdoms for 22 years, a period known as the Jacobean era, until his death. After the Union of the Crowns, he based himself in England (the largest of the three realms) from 1603, returning to Scotland only once, in 1617, and styled himself "King of Great Britain and Ireland". He was a major advocate of a single parliament for England and Scotland. In his reign, the Plantation of Ulster and English colonisation of the Americas began.

At 57 years and 246 days, James's reign in Scotland was the longest of any Scottish monarch. He achieved most of his aims in Scotland but faced great difficulties in England, including the Gunpowder Plot in 1605 and repeated conflicts with the English Parliament. Under James, the "Golden Age" of Elizabethan literature and drama continued, with writers such as William Shakespeare, John Donne, Ben Jonson, and Sir Francis Bacon contributing to a flourishing literary culture. James himself was a prolific writer, authoring works such as Daemonologie (1597), The True Law of Free Monarchies (1598), and Basilikon Doron (1599). He sponsored the translation of the Bible into English later named after him, the Authorized King James Version. Sir Anthony Weldon claimed that James had been termed "the wisest fool in Christendom", an epithet associated with his character ever since. Since the latter half of the 20th century, historians have tended to revise James's reputation and treat him as a serious and thoughtful monarch. He was strongly committed to a peace policy, and tried to avoid involvement in religious wars, especially the Thirty Years' War that devastated much of Central Europe. He tried but failed to prevent the rise of hawkish elements in the English Parliament who wanted war with Spain. He was succeeded by his second son, Charles.