Preben Christian Alexander von Magnus (25 February 1912 – 9 August 1973) was a Danish virologist who is known for his research on influenza, polio vaccination and monkeypox. He gave his name to the Von Magnus phenomenon. He represented Denmark at the 1959 Pugwash Conferences on Science and World Affairs where he explained that respiratory viruses such as influenza and the common cold were unsuitable as biological weapons. He became a Knight of the Order of the Dannebrog in 1965.