Math self-efficacy has been shown to predict math achievement and interest in a math-related career, such as one in science, technology, engineering, and mathematics (STEM). However, women consistently report lower math self-efficacy than men, contributing to gender disparities in upper-level math courses and the underrepresentation of women in STEM fields. Thus, it is crucial to understand what gender differences may exist in the development of math self-efficacy. Furthermore, with the proliferation of online classes in higher education, it is imperative to study math self-efficacy in this context. The purpose of this study was twofold. First, I investigated the relationships between the four sources of self-efficacy (i.e., mastery experiences, vicarious experiences, social persuasion, and physiological/emotional states) and the math self-efficacy of community college online math students. This investigation included identifying any differences in these relationships by gender. Second, I investigated the relationship between math self-efficacy of community college online math students and interest in pursuing a STEM career, including any differences in this relationship by gender. The study was implemented in a large, urban community college in the midwestern United States, and participants consisted of students enrolled in any online math course (i.e., asynchronous, synchronous, or blended). Data was collected using modified versions of previously validated instruments and analyzed using several regression models. The findings indicated that there are significant gender differences in the strengths of the sources of math self-efficacy. For community college online math students, physiological/emotional states was the most influential source of math self-efficacy, and it was even more influential for women than for men. Social persuasion was also more influential for women than for men. Additionally, the findings indicated that math self-efficacy predicts interest in a STEM career for women in community college online math classes but not for men. Implications of these findings for math education include the need for interventions to address math anxiety in community college online students and to provide ample positive feedback and encouragement. Fostering women's math self-efficacy may also help them develop interest in math-related careers and, in turn, help resolve the underrepresentation of women in STEM fields. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]