André-Louis Debierne (July 14, 1874, Paris - August 31, 1949, Paris) was a French chemist and the discoverer of the element actinium (1899).
Debierne, a student of Charles Friedel, was a close friend of Pierre and Marie Curie and was associated with their work. In 1899, he discovered the radioactive element actinium, as a result of continuing the work with pitchblende that the Curies had initiated.
After the death of Pierre Curie in 1906, Debierne helped Marie Curie carry on and worked with her in teaching and research.
In 1910, he and Marie Curie prepared radium in metallic form in visible amounts. They did not keep it metallic, however. Having demonstrated the metal's existence as a matter of scientific curiosity, they reconverted it into compounds with which they might continue their researches. Debierne and Marie curie isolated radium into a pure metal.