This thesis endeavors to answer the question, “What, if any, is the role of the designer in facilitating play?” I base my answer to this question on years of play studies, design projects, conversations with experts, classes, conferences, seminars, travel, and careful observation. I ran an extensive literature search on play theory, design, science, philosophy, and playwork, only to discover that there was little agreement on the matter of defining play. By reviewing the ‘cited by’ tables of online resources (lists of papers that cite a given article), I was able to find a contemporary definition in line with my own understanding of play, active frivolity, which I explain in Chapter 1. Working through a complex landscape of historical interpretations of play, Chapter 2 explains the evolution of contemporary play theories and concludes with what I call Omnidisciplinary Play Theory, a synthesis of Joe Frost’s Integrated Theory of Play and Nathaniel Gindele’s Naturalistic Philosophy of Play. Omnidisciplinary Play Theory is an instructive tool for understanding the phenomenon of play, and explains it in five ways: exemplars, motives, behaviors, content, and developmental correlates. Chapter 3 argues that play is a fundamental part of a complete human experience and should be treated as a human right rather than a leisurely privilege. This has important implications for designers, namely that their duty is to allow for the widest possible variety of play in an environment designed for such purpose. Implicit in this obligation is the need to respect the agency of prospective users as designers, builders, and directors of their own space. Chapter 4 describes how meritocracies are antithetical to play and are one of the major reasons our ethical obligation to provision play is beset with systemic, societal resistance. Chapter 5 describes how external goals of value such as education are also antithetical to play. It stipulates, however, that once primary agendas of players are met, external agendas may be covertly introduced as long as said agendas are not in conflict. Chapter 6 outlines the practical applicability of the theoretical, ethical, and philosophical perspectives covered in previous chapters by translating them into actionable design guidelines. The thesis concludes by suggesting that the role of the designer in facilitating play is to understand it deeply; engage in it; practice empathy; respect the agency of players; advocate for the right to play; provision time, space, materials, and permission so as to allow for the widest possible variety of play; design exemplary playscapes; consult over the lifetime of the project; and learn from its evolution.