Oersted was born at Rudkjöbing in Denmark and studied at Copenhagen University, where he received a PhD in 1799 for a thesis defending Kantian philosophy. To complete his scientific training he then traveled through Europe visiting the numerous physicists working on aspects of electricity. On his return to Denmark he started giving public lectures, which were so successful that, in 1806, he was offered a professorship at Copenhagen. Here he became well known as a great teacher and did much to raise the level of Danish science to that of the rest of Europe.

It was while lecturing that he actually first observed electromagnetism (although for years he had believed in its existence) by showing that a needle was deflected when brought close to a wire through which a current was flowing. By the summer of 1820 he had confirmed the existence of a circular magnetic field around the wire and published his results. They produced an enormous flurry of new activity in the scientific world, which up to that time had accepted Coulomb's opinion that electricity and magnetism were completely independent forces.