As the first son of Henry III, Edward was involved early in the political intrigues of his father's reign, which included an outright rebellion by the English barons. In 1259, he briefly sided with a baronial reform movement, supporting the Provisions of Oxford. After reconciliation with his father, however, he remained loyal throughout the subsequent armed conflict, known as the Second Barons' War. After the Battle of Lewes, Edward was hostage to the rebellious barons, but escaped after a few months and joined the fight against Simon de Montfort. Montfort was defeated at the Battle of Evesham in 1265, and within two years the rebellion was extinguished. With England pacified, Edward joined the Ninth Crusade to the Holy Land. The crusade accomplished little, and Edward was on his way home in 1272 when he was informed that his father had died. Making a slow return, he reached England in 1274 and was crowned at Westminster on 19 August.
After suppressing a minor rebellion in Wales in 1276–77, Edward responded to a second rebellion in 1282–83 with a full-scale war of conquest. After a successful campaign, Edward subjected Wales to English rule, built a series of castles and towns in the countryside and settled them with English people. Next, his efforts were directed towards Scotland. Initially invited to arbitrate a succession dispute, Edward claimed feudal suzerainty over the kingdom. The war that followed continued after Edward's death, even though the English seemed victorious at several points. Simultaneously, Edward I found himself at war with France (a Scottish ally) after the French king Philip IV had confiscated the duchy of Aquitaine, which until then had been held in personal union with the Kingdom of England. Although Edward recovered his duchy, this conflict relieved English military pressure against Scotland. At the same time there were problems at home. In the mid-1290s, extensive military campaigns required high levels of taxation, and Edward met with both lay and ecclesiastical opposition. These crises were initially averted, but issues remained unsettled. When the King died in 1307, he left to his son Edward II an ongoing war with Scotland and many financial and political problems.
Edward I was a tall man for his era, hence the nickname "Longshanks". He was temperamental, and this, along with his height, made him an intimidating man, and he often instilled fear in his contemporaries. Nevertheless, he held the respect of his subjects for the way he embodied the medieval ideal of kingship, as a soldier, an administrator and a man of faith. Modern historians are divided on their assessment of Edward I: while some have praised him for his contribution to the law and administration, others have criticised him for his uncompromising attitude towards his nobility. Currently, Edward I is credited with many accomplishments during his reign, including restoring royal authority after the reign of Henry III, establishing Parliament as a permanent institution and thereby also a functional system for raising taxes, and reforming the law through statutes. At the same time, he is also often criticised for other actions, such as his brutal conduct towards the Scots, and issuing the Edict of Expulsion in 1290, by which the Jews were expelled from England. The Edict remained in effect for the rest of the Middle Ages, and it was over 350 years until it was formally overturned under Oliver Cromwell.
Edward was born at the Palace of Westminster on the night of 17–18 June 1239, to King Henry III and Eleanor of Provence. Edward is an Anglo-Saxon name, and was not commonly given among the aristocracy of England after the Norman conquest, but Henry was devoted to the veneration of Edward the Confessor, and decided to name his firstborn son after the saint. Among his childhood friends was his cousin Henry of Almain, son of King Henry's brother Richard of Cornwall. Henry of Almain would remain a close companion of the prince, both through the civil war that followed, and later during the crusade. Edward was in the care of Hugh Giffard – father of the future Chancellor Godfrey Giffard – until Bartholomew Pecche took over at Giffard's death in 1246.
There were concerns about Edward's health as a child, and he fell ill in 1246, 1247, and 1251. Nonetheless, he became an imposing man; at 6 feet 2 inches (1.88 m) he towered over most of his contemporaries, and hence perhaps his epithet "Longshanks", meaning "long legs" or "long shins". The historian Michael Prestwich states that his "long arms gave him an advantage as a swordsman, long thighs one as a horseman. In youth, his curly hair was blond; in maturity it darkened, and in old age it turned white. His speech, despite a lisp, was said to be persuasive."