William James Stirling CBE FRS FInstP (4 February 1953 – 9 November 2018) was a physicist who served as the first Provost of Imperial College London.

In 2000 he became the first Director of the University's new Institute for Particle Physics Phenomenology (IPPP), which together with the Institute for Computational Cosmology, forms part of the Ogden Centre for Fundamental Physics, and before moving to Cambridge was Pro-Vice Chancellor (Research) from 2005 to 2008.

He was a member of the Physics Sub-Panel in two Research Assessment Exercises (2001 and 2008) and was Deputy Chair of the 2008 panel.

He was a member of the internationally renowned MSTW collaboration that studies the 'parton' structure of the proton.

In recognition of his contribution to particle physics research, Stirling was elected to the Fellowship of the Royal Society[6] in May 1999.