ABSTRACT In 1826 Marian Mason was introduced to British society as a callisthenic instructor. Trained by P.H. Clias, a gymnast who oversaw physical training in the military and navy, Mason is the first high profile female fitness coach in British history. Despite her importance as a landmark figure, Mason's contributions, and indeed life, remain relatively obscured from the historical record. Studying Mason's heyday in public life from 1826 to the early 1830s, this article provides the first substantive examination of Mason's life, her social networks and wealth and, critically, the monograph she published in 1826. While acknowledging Mason's role as an early female fitness coach, the article provides a deep reading of Mason's successes, focusing on her class and relationship advantages, her ability to court medical favour and shrewdness in addressing broader societal concerns. This article is less a biography and more an examination of the broader social and medical trends in early nineteenth century England, which created a space for people like Mason. The article presents a simple argument – Marian Mason was an early female fitness coach who, drawing on broader societal concerns about the body, created a niche for her career by leveraging her expertise and familial connections.