Cornelis (“Kees”) de Jager, the co-founder of the journal Solar Physics, passed away on 27 May 2021. He was an exemplary human being, a great scientist, and he had a large impact on our field. In this tribute, we first briefly summarize his life and career and then describe some of his solar activities, from his Ph.D. thesis on the hydrogen lines in 1952 to the book on cycle–climate relations that he completed last year.