The United Nations declared the period between 2022 and 2032 as the International Decade of Indigenous Languages due to the critical situation of many Indigenous languages around the world. My dissertation project responds to this declaration by studying the history of the Mvskoke language, an Indigenous language from the North American Southeast. By learning the Mvskoke language and combing numerous historical language sources, my project shows that language should be a fundamental part of how we understand Native sovereignty. From major political and diplomatic events to the everyday interactions between family members and communities who recognized each other as Muscogee, my project argues that Mvskoke speakers in the eighteenth and nineteenth centuries used language to structure their relationships and mutual obligations to one another. Not only does this project establish a new, language-based framework for Native sovereignty, but it also has important implications for modern Mvskoke language revitalization efforts. As I conducted archival research for this project, I joined my Mvskoke language instructor in creating an archive of historical Mvskoke language materials for teaching and language revitalization.