James Herriot is the pen name of James Alfred Wight, OBE, FRCVS also known as Alf Wight, an English veterinary surgeon and writer. Wight is best known for his semi-autobiographical stories, often referred to collectively as All Creatures Great and Small, a title used in some editions and in film and television adaptations.

In 1939, at the age of 23, he qualified as a veterinary surgeon with Glasgow Veterinary College. In January 1940, he took a brief job at a veterinary practice in Sunderland, but moved in July to work in a rural practice based in the town of Thirsk, Yorkshire, close to the Yorkshire Dales and North York Moors, where he was to remain for the rest of his life. The original practice is now a museum, "The World of James Herriot".

Wight intended for years to write a book, but with most of his time consumed by veterinary practice and family, his writing ambition went nowhere. Challenged by his wife, in 1966 (at the age of 50), he began writing. In 1969 Wight wrote If Only They Could Talk, the first of the now-famous series based on his life working as a vet and his training in the Royal Air Force during the Second World War. Owing in part to professional etiquette which at that time frowned on veterinary surgeons and other professionals from advertising their services, he took a pen name, choosing "James Herriot". If Only They Could Talk was published in the United Kingdom in 1970 by Michael Joseph Ltd, but sales were slow until Thomas McCormack, of St. Martin's Press in New York City, received a copy and arranged to have the first two books published as a single volume in the United States. The resulting book, titled All Creatures Great and Small, was an overnight success, spawning numerous sequels, movies, and a successful television adaptation.

In his books, Wight calls the town where he lives and works Darrowby, which he based largely on the towns of Thirsk and Sowerby. He also renamed Donald Sinclair and his brother Brian Sinclair as Siegfried and Tristan Farnon, respectively. Wight's books are only partially autobiographical. Many of the stories are only loosely based on real events or people, and thus can be considered primarily fiction.

The Herriot books are often described as "animal stories" (Wight himself was known to refer to them as his "little cat-and-dog stories"), and given that they are about the life of a country veterinarian, animals certainly play a significant role in most of the stories. Yet animals play a lesser, sometimes even a negligible role in many of Wight's tales: the overall theme of his stories is Yorkshire country life, with its people and their animals primary elements that provide its distinct character. Further, it is Wight's shrewd observations of persons, animals, and their close inter-relationship, which give his writing much of its savour. Wight was just as interested in their owners as he was in his patients, and his writing is, at root, an amiable but keen comment on the human condition. The Yorkshire animals provide the element of pain and drama; the role of their owners is to feel and express joy, sadness, sometimes triumph. The animal characters also prevent Wight's stories from becoming twee or melodramatic — animals, unlike some humans, do not pretend to be ailing, nor have they imaginary complaints and needless fears. Their ill-health is real, not the result of flaws in their character which they avoid mending. In an age of social uncertainties, when there seem to be no remedies for anything, Wight's stories of resolute grappling with mysterious bacterial foes or severe injuries have an almost heroic quality, giving the reader a sense of assurance, even hope. Best of all, James Herriot has an abundant humour about himself and his difficulties. He never feels superior to any living thing, and is ever eager to learn — about animal doctoring, and about his fellow human creature.