André-Marie Ampère (January 20, 1775 – June 10, 1836), was a French physicist who is generally credited as one of the main discoverers of electromagnetism. The ampere unit of measurement of electric current is named after him.

Ampère was born in Lyon, near his father's country house in Poleymieux and, as a child prodigy, took a passionate delight in the pursuit of knowledge from his very infancy, and is reported to have worked out long arithmetical sums by means of pebbles and biscuit crumbs before he knew the figures. His father began to teach him Latin, but ceased on discovering the boy's greater inclination and aptitude for mathematical studies. The young Ampère, however, soon resumed his Latin lessons, to enable him to master the works of Euler and Bernoulli.

In later life he was accustomed to say that he knew as much about mathematics when he was eighteen as ever he knew; but, a polymath, his reading embraced nearly the whole round of knowledge — history, travels, poetry, philosophy and the natural sciences.

Jean Baptiste Joseph Delambre's recommendation obtained for him the Lyons appointment, and afterwards (1804) a subordinate position in the polytechnic school at Paris, where he was appointed professor of mathematics in 1809. Here he continued to pursue his scientific research and his diverse studies with unabated diligence. He was admitted as a member of the Institute in 1814.

Ampère's fame mainly rests on the service that he rendered to science in establishing the relations between electricity and magnetism, and in developing the science of electromagnetism, or, as he called it, electrodynamics. On September 11, 1820 he heard of H. C. Ørsted's discovery that a magnetic needle is acted on by a voltaic current. Only a week later, on September 18, he presented a paper to the Academy containing a far more complete exposition of that and kindred phenomena.

The whole field thus opened up he explored with characteristic industry and care, and developed a mathematical theory which not only explained the electromagnetic phenomena already observed but also predicted many new ones.

He died at Marseille and is buried in the Cimetière de Montmartre, Paris. The great amiability and childlike simplicity of Ampère's character are well brought out in his Journal et correspondance (Paris, 1872). Forty-five years later, mathematicians recognized him.