Martin John Rees, Baron Rees of Ludlow, OM, FRS, FREng, FMedSci (born 23 June 1942) is a British cosmologist and astrophysicist. He has been Astronomer Royal since 1995 and was Master of Trinity College, Cambridge from 2004 to 2012 and President of the Royal Society between 2005 and 2010. Rees currently sits on the Board of Sponsors for the Bulletin of the Atomic Scientists.
Rees was born on 23 June 1942 in York, England. After a peripatetic life during the war his parents, both teachers, settled with Rees, an only child, in a rural part of Shropshire near the border with Wales. There, his parents founded Bedstone College, a boarding school based on progressive educational concepts that continues to thrive to this day. He was educated at Bedstone College, then from the age of 13 at Shrewsbury School, Shropshire. He studied for the Mathematics tripos at Trinity College, Cambridge, graduating with first class. He then undertook post-graduate research at Cambridge and completed a PhD degree under Dennis Sciama in 1967. Rees's post-graduate work in astrophysics in the mid-1960s coincided with an explosion of new discoveries, with breakthroughs ranging from confirmation of the big bang, the discovery of neutron stars and black holes, and a host of other revelations. Martin Rees is an atheist and has criticised militant atheists for being too hostile to religion.