William Harvey (1 April 1578 – 3 June 1657) was an English physician. He was the first to describe completely and in detail the systemic circulation and properties of blood being pumped to the body by the heart,.

William Harvey was born in Folkestone, Kent on 1 April 1578. Harvey was educated at King's College, Canterbury and then at Cambridge University. He then studied medicine at the University of Padua in Italy, where the scientist and surgeon Hieronymus Fabricius tutored him. Fabricius, his tutor, who was fascinated by anatomy, recognised that the veins in the human body had one-way valves, but was puzzled as to their function. Most people of the day believed that food was converted into blood by the liver, then was consumed as fuel by the body. Harvey knew this was untrue through his firsthand observations of human and animal dissections.

His career was helped by his marriage to Elizabeth Browne, daughter of Elizabeth I's physician, in 1604. In 1607, he became a fellow of the Royal College of Physicians and, in 1609, was appointed physician to St Bartholomew's Hospital. In 1618, he became physician to Elizabeth's successor James I and to James' son Charles when he became king. Both James and Charles took a close interest in and encouraged Harvey's research.

Harvey's research was furthered through the dissection of animals. When Harvey removed the beating heart from a living animal, it continued to beat, thus acting as a pump, not a sucking organ. Harvey also used mathematical data to prove that the blood was not being consumed. Removal of the blood from human cadavers (dead bodies) showed that the heart could hold roughly two ounces of blood. By calculating the number of heartbeats in a day and multiplying this by two ounces, he showed that the amount of blood pumped was far greater than the amount that the body could possibly make. He based this figure on how much food and liquids a person could eat during a day He first revealed his findings at the College of Physicians in 1616, and in 1628 he published his theories in a book entitled 'Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus' ('An Anatomical Study of the Motion of the Heart and of the Blood in Animals')