During the 1980s and 1990s, E.P. Thompson’s once-celebrated approach to social history came to be regarded as little more than an unstable half-way house between analytical and structuralist Marxism, on the one hand, and post-structuralism on the other. Critics on both sides maintained that “experience” and agency could not be analytically privileged without fatally undermining the theoretical foundations of historical materialism itself. This article recovers Thompson for historical materialism by demonstrating that the profound theoretical contributions of his work have yet to be fully recognised and explored. Some of the blame for this must lie with Thompson himself, for he never fully reconciled the different understandings of “class” sprinkled throughout his oeuvre, nor did he systematically investigate the broad, theoretical implications that his work held for the abstract propositions of classical Marxism. I argue that Thompson’s concept of class clarifies two particular problems in the classical Marxist tradition. The first is the relationship between social being and consciousness, which Thompson re-conceives as a dialectical interaction through the mediation of “experience”. The second is the historical origin of the working class through a process of making, a concern which was left largely unaddressed in the classical canon. Thompson’s central insight that class relations are distinct from production relations and require a very specific kind of “horizontal solidarity” between persons in similar class “situations”, is at once a crucial theoretical extension of Marxism and an affirmation of historical materialism’s explanatory potential.