Abstract: This chapter examines Margaret H. Marshall, the first female Chief Justice of the Supreme Judicial Court of Massachusetts. Best known for her Court's ground-breaking 2003 decision in Goodridge v Department of Public Health, upholding the right under the Massachusetts State Constitution for same-sex couples to marry, Marshall's work brought together deep principles—of equal human dignity and judicial independence—with a well-honed sense of prudence. To her adjudicatory role she brought fine legal craft. In stewarding the state courts, she brought forward-looking leadership skills as well as a commitment to improving the entire justice system. Her commitments to constitutional democracy were reflected not only in her opinions and her work to improve the administration of justice but also in her efforts to advance gender equality in the Bar. She rightly deserves to be viewed as among the judicial heroines of the late 20th and early 21st centuries.