Sarah George Bagley (April 19, 1805 – 1883-1895?) was an advocate for women's rights and one of the most important labor leaders in New England during the 1840s. An advocate of shorter workdays for factory operatives and mechanics, she campaigned to make ten hours of labor per day the maximum in Massachusetts. Her activities in support of the mill workers in Lowell, Massachusetts put her in contact with a broader network of reformers in areas of women’s rights, communitarianism, abolition, peace, prison reform, and health reform. Sarah Bagley and her coworkers became familiar with middle-class reform activities, demonstrating the ways in which working people embraced this reform impulse as they transformed and critiqued some of its key elements. Sarah’s activities within the labor movement reveal many of the tensions that underlay relations between male and female working people as well as the constraints of gender that female activists had to overcome.