The Wars of the Three Kingdoms (sometimes known as the Wars of the Three Nations) form an intertwined series of conflicts that take place in Scotland, Ireland, and England between 1639 and 1651 after these three countries have come under the "Personal Rule" of the same monarch.

The English Civil War has become the best-known of these conflicts.

The wars are the outcome of tensions between king and subjects over religious and civil issues.

Religious disputes center on whether religion is to be dictated by the monarch or the choice of the subject, who has a direct relationship with God.

The related civil questions are to what extent the king's rule is constrained by parliaments — in particular his right to raise taxes and armed forces without consent.

In addition, the wars also have an element of national conflict, as Ireland and Scotland rebel against England's primacy within the Three Kingdoms.

The victory of the English Parliament — ultimately under Oliver Cromwell — over the King, the Irish and the Scots helps to determine the future of Great Britain as a constitutional monarchy with political power centered on London.

The Wars of the Three Kingdoms also parallel a number of similar conflicts at the same time in Europe — such as the Fronde in France and the rebellions of the Netherlands, Catalonia and Portugal against Spanish rule.

The Wars include the Bishops' Wars of 1639 and 1640, the Scottish Civil War of 1644–1645; the Irish Rebellion of 1641, Confederate Ireland, 1642–1649 and the Cromwellian conquest of Ireland in 1649 (collectively the Irish Confederate Wars); and the First, Second and Third English Civil Wars of 1642–1646, 1648–1649 and 1650–1651.The naming of these linked conflicts as the Wars of the Three Kingdoms represents a trend by recent historians aiming to take a unified overview rather than treating some of the conflicts as mere background to the English Civil War.

Some, such as Gaunt or Plant, have labeled them the British Civil Wars, but this led to confusion, as the kingdoms did not become a single political entity until the Act of Union 1800.