A strongly deterministic theory of physics is one that permits exactly one possible history of the universe. In the words of Penrose (1990), "it is not just a matter of the future being determined by the past; the entire history of the universe is fixed, according to some precise mathematical scheme, for all time.” Such an extraordinary feature may appear unattainable in any realistic theory of physics. First, Chen proposes a definition of strong determinism and explain how it differs from standard determinism and super-determinism. An important consideration is the simplicity of fundamental laws. Next, Chen discusses its attractions, implications, and two toy examples. The possibility of strong determinism has significant consequences for explanation, causation, prediction, fundamental properties, free will, and modality. Finally, Chen shows that Everettian quantum mechanics, with a new version of the Past Hypothesis, provides an easy route to strong determinism. On a theory that Chen calls the Everettian Wentaculus, the quantum state of the multiverse is a fundamental mixed state with exactly one possible history. As a consequence of physical laws, the history of the multiverse could not have been different. The Everttian Wentaculus is, as far as Chen knows, the first realistic example of a strongly deterministic (and simple) physical theory. If it is empirically equivalent to other quantum theories, we can never empirically find out whether or not our world is strongly deterministic. Even if strong determinism fails to be true, it is closer to the actual world than we have presumed, with implications for some of the central topics in philosophy and foundations of physics.