John Newton was born on 24 July 1725 in Wapping, London. Press-ganged into the Royal Navy at nineteen, he served on the West African slave coast, was himself briefly enslaved to a Sierra Leone trader's wife, and then rose to captain three slave voyages of his own between 1750 and 1754.
On 10 March 1748, homeward-bound from West Africa aboard the Greyhound, his ship was nearly lost in a North Atlantic storm. Newton — reading Thomas à Kempis in the flooded hold — cried out to a God he had spent years mocking, and marked the date for the rest of his life as his spiritual birthday.
He continued in the slave trade for another six years — a fact he later called the enduring shame of his life — before an epileptic collapse in 1754 ended his sea career. Ordained in the Church of England in 1764, he became curate at Olney, Buckinghamshire, and there collaborated with the poet William Cowper on the Olney Hymns (1779).
"'Amazing Grace' was written as the accompanying text to Newton's sermon for the New Year's Day 1773 service, based on 1 Chronicles 17:16–17: "who am I, O Lord God, and what is my house, that thou hast brought me hitherto?" It was published in the Olney Hymns book six years later."
For its first half-century the hymn was sung to several different melodies in Britain and America. The tune it now shares — "New Britain", a Scottish or Appalachian folk melody — was fixed only in 1835, when the American Baptist compiler William Walker wedded text and tune in his Southern Harmony shape-note collection.
Newton spent his last years testifying before the House of Commons in support of William Wilberforce's 1807 Slave Trade Act, publicly repenting the trade he had once run. He died in December 1807, months after the Act became law, and is buried at Olney beside his wife Mary.