St. Aelred, whose name is also written Ælred, Ailred, Æthelred, and Ethelred, was one of three sons of Eilaf, priest of St Andrew's at Hexham. He was born in Hexham, Northumbria, Northern England in 1109.

Being educated in learning and piety at Durham, around 1130, he was invited by St. David, the pious King of Scotland, to his court, made seneschal of his household and was highly esteemed both by him and the courtiers.

At the age of twenty-four, in 1133, he became a monk under William, the first abbot of Rievaulx and disciple of St. Bernard. In spite of the delicacy of his body, he set himself cheerfully to practice the greatest austerities and employed much of his time in prayer and reading. His heart turned with great ardor to the love of God and this made him feel all the Cistercian disciplines as sweetness and light. He had been much delighted, in his youth, with reading Cicero; but, after his conversion, found that author and all others, tedious and bitter, unless they wrote of the word of God. This he records in the preface to his book 'On Spiritual Friendship'.

St. Aelred was held in high esteem at Rievaulx and was chosen, in 1142, to travel to Rome as an envoy in the disputed election of William FitzHerbert to the Archiepiscopate of York. Upon his return, he was made Novicemaster and, the following year, he was made abbot of a new monastery of his order, founded by William, Earl of Lincoln, at Revesby in Lincolnshire. Only four years later, he was recalled to the same position at Rievaulx. The house prospered under his rule to such an extent that it became the largest of its time in England. It was home to 150 monks and 500 lay brothers; and five daughter houses were established on both sides of the Northern border. Describing the lives of his brethren, Aelred recorded that they drank nothing but water, ate little, labored hard, slept little - and on hard boards - never spoke, except to their superiors on necessary occasions, and loved prayer.

Aelred wrote several influential books on spirituality, among them Speculum caritatis ("The Mirror of Charity", reportedly written at the request of Bernard of Clairvaux) and De spiritali amicitia ("On Spiritual Friendship"). He also wrote seven works of history, addressing two of them to Henry II of England, advising him how to be a good king and declaring him to be the true descendent of Anglo-Saxon kings. Until the twentieth century, Aelred was generally known as a historian rather than as a spiritual writer; for many centuries his most famous work was his Life of Saint Edward, King and Confessor.

Through his friends and his writings, Aelred became a figure of national importance. He was chosen to preach at Westminster Abbey during the translation of St. Edward the Confessor in 1163 and subsequently wrote his well-known life of this man. Other works include a Life of St. Ninian, the Saints of Hexham and Sermons on Isaiah which are often considered his finest.

Towards the end of his life, ill-health forced Aelred to live in a small hut near the infirmary at Rievaulx. He was now rarely able to travel. Though, occasionally, he managed to visit his friend, St. Godric, on his way north to his Scottish foundations. He died on the 12th January, 1167 and was buried in the Chapter House at Rievaulx. He was never formally canonized, but a local cult, approved by the Cistercians, quickly grew up around him and his body was translated to a superb gold and silver shrine behind the high-altar.