Hilary Greaves (born 29 September 1978) is a British philosopher. She is currently a professor at the University of Oxford and the director of the Global Priorities Institute.

Greaves earned a BA in philosophy and physics from Oxford and a PhD in philosophy from Rutgers. Her doctoral thesis, completed under the supervision of Frank Arntzenius, was "Spacetime symmetries and the CPT theorem" (Greaves 2012). Prior to her current professorship, she held appointments at Merton and Somerville Colleges.

Greaves’ current work is on issues related to global priorities research. Her research interests include moral philosophy (including foundational issues in consequentialism, interpersonal aggregation, population ethics, and moral uncertainty), formal epistemology, and the philosophy of physics.