Lise Meitner (/ ˈ l iː z ə ˈ m aɪ t n ər / LEE -zə MYTE -nər, German: [ˈliːzə ˈmaɪtnɐ] ; born Elise Meitner, 7 November 1878 – 27 October 1968) was an Austrian physicist who was instrumental in the discovery of protactinium and nuclear fission.