Charles Leroy Ellenberger (born 1942, known as C. Leroy) is perhaps best known as a one-time advocate, but now a critic of, controversial writer Immanuel Velikovsky and his works on catastrophism. He first read Worlds in Collision in 1969. In 1979, he became a contributing editor (and later Senior Editor & Executive Secretary) to the Velikovsky-inspired Kronos journal, and has contributed material to many other publications. In 1980 he was selected by the editor of Astronomy magazine to debate James Oberg on Velikovsky.