Einstein's theories of special relativity and general relativity form a core part of today's undergraduate (or masters-level) physics curriculum. this is a supplementary problem book or student's manual, consisting of 150 problems in each of special and general relativity. the problems, which have been developed, tested and refined by the authors over the past two decades, are a mixture of short-form and multi-part extended problems, with hints provided where appropriate. complete solutions are elaborated for every problem, in a different section of the book; some solutions include brief discussions on their physical or historical significance. designed as a companion text to complement a main relativity textbook, it does not assume access to any specific textbook. this is a helpful resource for advanced students, for self-study, a source of problems for university teaching assistants, or as inspiration for instructors and examiners constructing problems for their lectures, homework or exams.