Carl Oluf Jensen (18 March 1864 – 3 September 1934) was a Danish veterinarian who contributed to the study of cancer through animal studies on cancer induction that continue to be used in research cultures and was well known as Jensen sarcoma cells. He also wrote an influential text on dairy bacteriology. Jensen married Maria Magdalene Schmit in 1890. He was a member of the Royal Danish Society of Sciences from 1903. He received the Walker Prize of 1906 for his work on cancer. He died suddenly from an apoplexy while on vacation in Middelfart.