Ruth Alexandra Britto-Pacumio is an American mathematical physicist whose research topics include black holes, Yang–Mills theory, and the theory of Feynman integrals; with Freddy Cachazo, Bo Feng, and Edward Witten she is one of the namesakes of the BCFW recursion relations for computing scattering amplitudes. She is an associate professor in mathematics and theoretical physics at Trinity College Dublin, and is also affiliated with the Institut de Physique Théorique of CEA Saclay.