Timothy John O'Brien (born 31 March 1964) is a British astronomer, currently working at the University of Manchester as Professor of Astrophysics.

He grew up in Castleton, Greater Manchester in the Metropolitan Borough of Rochdale.

He studied Physics and Astrophysics at Queen Mary College and completed his PhD at the University of Manchester between 1985 and 1988.

[8] His research is primarily in the area of novae (thermonuclear explosions on white dwarf stars in binary star systems) and includes both theoretical work and observations using telescopes around the world and in space working across the electromagnetic spectrum.

[9][10] O'Brien is married to Professor Teresa Anderson (born 1 December 1962).