Tort law is the body of state common law that decides when one person must pay for harm done to another outside of contract. This guide walks the three families of tort liability — intentional torts, negligence, and strict liability — and takes the negligence prima facie case apart element by element: duty and its policy roots in Palsgraf, breach under the reasonable-person standard and the Hand formula, negligence per se and res ipsa loquitur, actual causation and the multiple-cause problems that break the but-for test, proximate cause and superseding events, and damages including the economic-loss rule. It then covers the affirmative defenses where states genuinely diverge — contributory negligence survives in only a handful of jurisdictions while the rest have adopted pure or modified comparative fault — plus assumption of risk, premises-liability entrant categories, the intentional torts and their privileges, strict liability for abnormally dangerous activities and animals, vicarious liability and the scope-of-employment line, compensatory and punitive damages under the Gore/State Farm framework, wrongful death and survival actions, and limitations and repose. Two running hypotheticals — a supermarket slip-and-fall and a two-car collision — are carried through the analysis. Because tort law is overwhelmingly state law, this guide teaches the majority rule and the Restatement framework and flags the divergences rather than asserting a single national rule.