Hazlitt came of Irish Protestant stock, and of a branch of it which moved in the reign of George I from the county of Antrim to Tipperary. His father went to the University of Glasgow (where he was contemporary with Adam Smith), graduated in about 1761, became a Unitarian, joined their ministry, and crossed over to England; being successively pastor at Wisbech in Cambridgeshire, at Marshfield in Gloucestershire, and at Maidstone. At Wisbech he married Grace Loftus, daughter of a farmer. Of their many children, only three survived infancy.

Childhood
William, the youngest of these, was born in Mitre Lane, Maidstone. From Maidstone the family moved in 1780 to Bandon, Co. Cork; and from Bandon in 1783 to America, where Mr. Hazlitt preached, lectured, and founded the First Unitarian Church at Boston. In 1786-1787 the family returned to England and took up their abode at Wem, in Shropshire. The elder son, John, was now old enough to choose a vocation, and became a miniature-painter. The second child, Peggy, had begun to paint also, amateurishly in oils. William, aged eight – a child out of whose recollection all memories of Bandon and of America (save the taste of barberries) soon faded – took his education at home and at a local school. His father intended him for the Unitarian ministry, and sent him to a seminary in London, Hackney College. He stayed there for only a year, but shortly after returning home, he decided to become a painter, a decision inspired somewhat by his brother's career. He alternated between writer and painter, proving himself proficient in both fields, until finally he decided the rewards of painting – monetarily and mentally – were outweighed by those of writing and he left it behind as a career.

Adulthood
In 1798 Hazlitt was introduced to Samuel Taylor Coleridge and William Wordsworth. He was also interested in art, and visited his brother John, who was now apprenticed to Sir Joshua Reynolds. He became friendly with Charles and Mary Lamb, and in 1808 he married Sarah Stoddart, who was a friend of Mary's, and brother of John Stoddart, editor of The Times. They lived at Winterslow in Salisbury, but after three years he left her and began a journalistic career, writing for the Morning Chronicle, Edinburgh Review, The Times, etc. He published several volumes of essays, including The Round Table and Characters of Shakespeare's Plays, both in 1817. His best-known work is The Spirit of the Age (1825), a collection of portraits of his contemporaries, including Lamb, Coleridge, Wordsworth, Lord Byron, Jeremy Bentham, and Sir Walter Scott.

Famous for never losing his revolutionary principles, Hazlitt attacked those he saw as 'apostates' with the most rigour, seeing their move towards conservatism as a personal betrayal. He felt admiration for Edmund Burke and pity for Coleridge, but saved the most vitriol for Wordsworth and the revolutionary-turned poet laureate Robert Southey. He had an affair with Sarah Walker, a maid at his lodging house, which caused him to have something of a breakdown and publish all their correspondence in a pamphlet, Liber Amoris. This was seized upon by the right-wing press and was used to destroy his distinguished journalistic career with scandal.

Hazlitt put forward radical political thinking which was proto-socialist and well ahead of his time and was a strong supporter of Napoleon Bonaparte, writing a four-volume biography of him. He had his admirers, but was so against the institutions of the time that he became further and further disillusioned and removed from public life. He died in poverty on 18th September 1830 and is buried in St. Anne’s Churchyard, Soho, London.

Works
An Essay on the Principles of Human Action(1805)
Lectures on the Literature of the Age of Elizabeth and Characters of Shakespear's Plays (1817)
Lectures on the English Poets (1818)
Lectures on the English Comic Writers (1819)
The Spirit of the Age (1825)