Sir Humphry Davy (December 17, 1778 - May 29, 1829), often incorrectly spelled Humphrey, was an English chemist.

He was born in Penzance, Cornwall, England.

Davy became well known owing to his experiences with the physiological action of some gases, including laughing gas (nitrous oxide). In 1801 he was nominated professor at the Royal Institution of Great Britain and member of the Royal Society that he would later preside over.

In 1800, Alessandro Volta introduced the first electric pile or battery. Davy used this electric battery to separate salts by what is now known as electrolysis. With many batteries in series he was able to separate elemental potassium and sodium in 1807 and calcium, strontium, barium, and magnesium in 1808. He also showed that oxygen could not be obtained from the substance known as oxymuriatic acid and proved the substance to be an element, which he named chlorine. He also studied the energies involved in separating these salts, which is now the field of electrochemistry.

In 1812 he was knighted, gave a farewell lecture to the Royal Institution, and married a wealthy widow. After a long vacation in Europe, he went on to produce the Davy lamp which was used by miners.

In 1824 he proposed and eventually mounted chunks of iron to the hull of a copper clad ship in the first use of cathodic protection.

Davy died in Geneva, Switzerland.

His laboratory assistant Michael Faraday went on to enhance his work and in the end became more famous and influential.