This guide covers parentage law end to end, for practitioners and for parents trying to understand their own status. Parts 1 and 2 explain why parentage is the predicate for every other family right, then set out the four routes to legal parenthood ranked by how durable each one actually is. Parts 3 through 5 cover the marital presumption, voluntary acknowledgments and the federal requirements that make them judgments, and adjudication, genetic testing, and the default judgment problem that produces a large share of incorrect orders. Parts 6 and 7 cover functional and intended-parent doctrines, assisted reproduction, and surrogacy, where the paperwork is the parentage. Part 8 covers disestablishment and the reasons it so often fails. Parts 9 and 10 cover competing presumptions, standing, deadlines, and putative father registries. Parts 11 and 12 cover the collateral consequences across support, child welfare, custody jurisdiction, immigration, and estates, and the drafting that makes a parent-child relationship secure across state lines.