John Mark Ramseyer (born 1954) is the Mitsubishi professor of Japanese Legal Studies at Harvard Law School. He is the author of over 10 books and 50 articles in scholarly journals. He is co-author of one of the leading corporations casebooks, Klein, Ramseyer & Bainbridge, Business Associations, Cases and Materials on Agency, Partnerships, LLCs, and Corporations, now in its 10th edition. In 2018 he was awarded Japan's Order of the Rising Sun, Gold Rays with Neck Ribbon in recognition of "his extensive contributions to the development of Japanese studies in the U.S. and the promotion of understanding toward Japanese society and culture."

In 2021, Ramseyer came under scrutiny for a preprint article released by the International Review of Law and Economics which, drawing from contracts, argued that comfort women conscripted under Japanese imperial rule were primarily voluntary prostitutes.