Friedrich Ernst Dorn (27 July 1848 – 16 December 1916) was a German physicist who was the first to discover that a radioactive substance, later named radon, is emitted from radium.

In 1885, at Halle University, Dorn took over the position of personal ordinarius professor for theoretical physics from Anton Oberbeck.

Dorn's previous duties were assumed by Carl Schmidt, who had been a Privatdozent and was called as an extraordinarius professor for theoretical physics.

[4] In 1900, Dorn published a paper in which he described experiments that repeated and extended some earlier work on thorium by Ernest Rutherford.

Dorn verified Rutherford's observation that a radioactive material was emitted by thorium, and discovered that a similar emission arose from the element radium.