Johannes A. van Paradijs (9 June 1946 – 2 November 1999) was a Dutch high-energy astrophysicist.

Van Paradijs determined the first mass of a neutron star, the X-ray pulsar Vela X-1 in 1975.

[2] Van Paradijs obtained his PhD at the University of Amsterdam, Netherlands, in 1975, working on cool giant stars.

His thesis was entitled "Studies of line spectra of G- and K-type stars"[4] and his supervisor was David Koelbloed.

He published over 400 scientific papers, including many with long-time collaborator Walter Lewin of MIT.