The Battle of Turnham Green took place on 13 November 1642 near the village of Turnham Green, at the end of the first campaigning season of the First English Civil War. The battle resulted in a standoff between the forces of King Charles I and the much larger Parliamentarian army under the command of the Earl of Essex. In blocking the Royalist army's way to London immediately, however, the Parliamentarians gained an important strategic victory as the standoff forced Charles and his army to retreat to Oxford for secure winter quarters.

The First English Civil War was fought in England and Wales, from August 1642 to June 1646. It forms one of the conflicts known collectively as the 1638 to 1651 Wars of the Three Kingdoms, which also took place in Scotland and Ireland. These include the 1638 to 1640 Bishops' Wars, the Irish Confederate Wars, the Second English Civil War, the Third English Civil War, and the Cromwellian conquest of Ireland. It is estimated that from 1638 to 1651, 15–20% of all adult males in England and Wales served in the military, and around 4% of the total population died from war-related causes, compared to 2.23% in World War I. These figures are important in understanding the impact of the conflict on society, and the bitterness it engendered.In the political conflict leading up to the war, the vast majority supported the institution of monarchy, but disagreed on who held ultimate authority. Royalists generally supported the primacy of Charles I over Parliament, while their Parliamentarian opponents backed constitutional monarchy. However, this simplifies a very complex reality; many tried to avoid taking sides or went to war with great reluctance and individual choices often came down to personal loyalties.

In August 1642, both sides expected the conflict to be settled by a single battle, but it soon became clear this was not the case. Royalist success in 1643 led to a military alliance between Parliament and the Scots Covenanters, and winning a series of battles in 1644, the most significant being the Battle of Marston Moor. The formation of the New Model Army gave Parliament the first professional military force in England, and their success at Naseby in June 1645 proved decisive. The war ended with victory for the Parliamentarian alliance in June 1646 and Charles in custody, but his refusal to agree significant concessions and divisions among his opponents led to the Second English Civil War in 1648.