Inder Bir Singh Passi (I.B.S. Passi) is an Indian mathematician who specialised in algebra.
He was awarded in 1983 the Shanti Swarup Bhatnagar Prize for Science and Technology, the highest science award in India, in the mathematical sciences category. Prof. Passi is a noted group-theorist in India, has made significant contribution to certain aspects of theory of groups specially to the study of group rings. His results on the dimension subgroups, augmentation powers in group rings, and related problems have received wide recognition. His 1979 monograph summarizing the state of the subject is a basic reference source.