Edward III (13 November 1312 – 21 June 1377) was King of England and Lord of Ireland from January 1327 until his death; he is noted for his military success and for restoring royal authority after the disastrous and unorthodox reign of his father, Edward II. Edward III transformed the Kingdom of England into one of the most formidable military powers in Europe. His long reign of 50 years was the second longest in medieval England (after that of his great-grandfather Henry III) and saw vital developments in legislation and government, in particular the evolution of the English parliament, as well as the ravages of the Black Death.

Edward was crowned at age fourteen after his father was deposed by his mother, Isabella of France, and her lover Roger Mortimer. At age seventeen he led a successful coup d'état against Mortimer, the de facto ruler of the country, and began his personal reign. After a successful campaign in Scotland he declared himself rightful heir to the French throne in 1337. This started what became known as the Hundred Years' War. Following some initial setbacks, this first phase of the war went exceptionally well for England; victories at Crécy and Poitiers led to the highly favourable Treaty of Brétigny, in which England made territorial gains, and Edward renounced his claim to the French throne. This phase would become known as the Edwardian War. Edward's later years were marked by international failure and domestic strife, largely as a result of his inactivity and poor health.

Edward III was a temperamental man but capable of unusual clemency. He was in many ways a conventional king whose main interest was warfare. Admired in his own time and for centuries after, Edward was denounced as an irresponsible adventurer by later Whig historians such as William Stubbs. This view has been challenged recently and modern historians credit him with some significant achievements.

Edward was born at Windsor Castle on 13 November 1312, and was often referred to as Edward of Windsor in his early years. The reign of his father, Edward II, was a particularly problematic period of English history. One source of contention was the king's inactivity, and repeated failure, in the ongoing war with Scotland. Another controversial issue was the king's exclusive patronage of a small group of royal favourites. The birth of a male heir in 1312 temporarily improved Edward II's position in relation to the baronial opposition. To bolster further the independent prestige of the young prince, the king had him created Earl of Chester at only twelve days of age.

In 1325, Edward II was faced with a demand from his brother-in-law, Charles IV of France, to perform homage for the English Duchy of Aquitaine. Edward was reluctant to leave the country, as discontent was once again brewing domestically, particularly over his relationship with the favourite Hugh Despenser the Younger. Instead, he had his son Edward created Duke of Aquitaine in his place and sent him to France to perform the homage. The young Edward was accompanied by his mother Isabella, who was the sister of King Charles, and was meant to negotiate a peace treaty with the French. While in France, Isabella conspired with the exiled Roger Mortimer to have Edward deposed. To build up diplomatic and military support for the venture, Isabella had her son engaged to the twelve-year-old Philippa of Hainault. An invasion of England was launched and Edward II's forces deserted him completely. Isabella and Mortimer summoned a parliament, and the king was forced to relinquish the throne to his son, who was proclaimed king in London on 25 January 1327. The new king was crowned as Edward III at Westminster Abbey on 1 February at the age of 14.