The Battle of Worcester took place on 3 September 1651 in and around the city of Worcester, England and was the last major battle of the 1642 to 1651 Wars of the Three Kingdoms. A Parliamentarian army of around 28,000 under Oliver Cromwell defeated a largely Scottish Royalist force of 16,000 led by Charles II of England and Scotland.

The Royalists took up defensive positions in and around the city of Worcester. The area of the battle was bisected by the River Severn, with the River Teme forming an additional obstacle to the south-west of Worcester. Cromwell divided his army into two main sections, divided by the Severn, in order to attack from both the east and south-west. There was fierce fighting at river crossing points and two dangerous sorties by the Royalists against the eastern Parliamentary force were beaten back. Following the storming of a major redoubt to the east of the city, the Parliamentarians entered Worcester and organised Royalist resistance collapsed. Charles II was able to escape capture.

The King was aided by Scottish allies and was attempting to regain the throne that had been lost when his father Charles I was executed. The commander of the Scots, David Leslie, supported the plan of fighting in Scotland, where royal support was strongest. Charles, however, insisted on making war in England. He calculated that Cromwell's campaign north of the River Forth would allow the main Scottish Royalist army which was south of the Forth to steal the march on the Roundhead New Model Army in a race to London. He hoped to rally not merely the old faithful Royalists, but also the overwhelming numerical strength of the English Presbyterians to his standard. He calculated that his alliance with the Scottish Presbyterian Covenanters and his signing of the Solemn League and Covenant would encourage English Presbyterians to support him against the English Independent faction which had grown in power over the last few years. The Royalist army was kept well in hand, no excesses were allowed, and in a week the Royalists covered 150 miles in marked contrast to the Duke of Hamilton's ill-fated expedition of 1648. On 8 August the troops were given a well-earned rest between Penrith and Kendal. The exact location is marked by a stone monument at Black Dub on Crosby Ravensworth Fell near Shap, Cumbria (OS Grid Ref : NY 604108). An inscription on the monument reads "Here at Black Dub; the source of the Livennet, King Charles II regaled his army and drank of the water on his march from Scotland. August 8th 1651"

However the Royalists were mistaken in supposing that the enemy was unaware. Everything had been foreseen both by Cromwell and by the Council of State in Westminster. The latter had called out the greater part of the militia on 7 August. Lieutenant-General Charles Fleetwood began to draw together the midland contingents at Banbury. The London trained-bands turned out for field service no fewer than 14,000 strong. Every suspected Royalist was closely watched, and the magazines of arms in the country-houses of the gentry were for the most part removed into the strong places. On his part Cromwell had quietly made his preparations. Perth passed into his hands on 2 August and he brought back his army to Leith by 5 August. Thence he dispatched Lieutenant-General John Lambert with a cavalry corps to harass the invaders. Major-General Thomas Harrison was already at Newcastle picking the best of the county mounted-troops to add to his own regulars. On 9 August, Charles was at Kendal, Lambert hovering in his rear, and Harrison marching swiftly to bar his way at the Mersey. Thomas Fairfax emerged for a moment from his retirement to organize the Yorkshire levies, and the best of these as well as of the Lancashire, Cheshire and Staffordshire militias were directed upon Warrington, which Harrison reached on 15 August, a few hours in front of Charles's advanced guard. Lambert too, slipping round the left flank of the enemy, joined Harrison, and the English fell back (16 August), slowly and without letting themselves be drawn into a fight, along the London road.

Cromwell meanwhile, leaving George Monck with the least efficient regiments to carry on the war in Scotland, had reached the river Tyne in seven days, and thence, marching 20 miles (32 km) a day in extreme heat with the country people carrying their arms and equipment, the regulars entered Ferrybridge on 19 August, at which date Lambert, Harrison and the north-western militia were about Congleton. It seemed probable that a great battle would take place between Lichfield and Coventry on or just after 25 August and that Cromwell, Harrison, Lambert and Fleetwood would all take part in it but the scene and the date of the denouement were changed by the Royalists' movements. Shortly after leaving Warrington the young king had resolved to abandon the direct march on London and to make for the Severn valley, where his father had found the most constant and the most numerous adherents in the first war, and which had been the centre of gravity of the English Royalist movement of 1648.

Sir Edward Massey, formerly the Parliamentary governor of Gloucester, was now with Charles, and it was hoped that he would induce his fellow Presbyterians to take arms. The military quality of the Welsh border Royalists was well proved, that of the Gloucestershire Presbyterians not less so, and, in basing himself on Gloucester and Worcester as his father had done on Oxford, Charles II hoped, naturally, to deal with the Independent faction minority of the English people more effectually than Charles I had earlier dealt with the majority of the people of England who had supported the Parliamentary cause. However the pure Royalism which now ruled in the invading army could not alter the fact that it was a foreign, Scottish, army, and it was not merely an Independent faction but all England that united against it.

Charles arrived at Worcester on 22 August and spent five days in resting the troops, preparing for further operations, and gathering and arming the few recruits who came in. The delay was to prove fatal; it was a necessity of the case foreseen and accepted when the march to Worcester had been decided upon, and had the other course, that of marching on London via Lichfield, been taken the battle would have been fought three days earlier with the same result. Worcester itself had no particular claim to being loyal to the King. Throughout the First Civil War it had taken the pragmatic position of declaring loyalty to whichever side had been in occupation. The epithet 'Faithful City' arose out of a cynical (and unsuccessful) claim at the Restoration for compensation from the new king.

Cromwell, the lord general, had during his march south thrown out successively two flying columns under Colonel Robert Lilburne to deal with the Lancashire Royalists under the Earl of Derby. Lilburne entirely routed a Lancashire detachment of the enemy on their way to join the main Royalist army at the Battle of Wigan Lane on 25 August and as affairs turned out Cromwell merely shifted the area of his concentration two marches to the south-west, to Evesham. Early on 28 August, Lambert's brigade made a surprise crossing of the Severn at Upton, 6 miles (9.7 km) below Worcester. In the action which followed Massey was severely wounded and he and his men were forced to retreat northwards along the west bank of the Severn towards the river Teme and Worcester. Fleetwood followed Lambert with reinforcements and orders to advance north towards the Teme. This western envelopment severed the Royalists' lines of communications to Wales and the western counties of England. The Royalists were now only 16,000 strong with no hope of significant reinforcements and disheartened by the apathy with which they had been received in districts formerly all their own. Cromwell, for the only time in his military career, had a two-to-one numerical superiority.