Men comprise the majority within science, technology, engineering, and math (STEM), yet efforts to generate more inclusive environments within these disciplinary cultures often focus their attention on shifting women's behaviors. However, a limited number of formal training initiatives have demonstrated the efficacy of men allies for their women faculty counterparts. No such programs exist for supporting students, despite literature that highlights the impact of faculty on the experience of their students. Using social identity theory, this study examines the motivations, perceptions, and experiences of men faculty allies for undergraduate women in STEM. The data demonstrate that participants' behaviors can be categorized into one of three groups related to their levels of allyship: 1) educators; 2) pragmatists; and 3) dis-engagers. Whereas educators aimed to educate their colleagues on the harmful effects of some behaviors, pragmatists primarily concentrated their efforts on supporting women students. Dis-engagers, on the other hand, intentionally ignored problematic behaviors from colleagues, rationalizing instead that colleagues would eventually retire. Findings suggest that leveraging men, as the majority population, may be an effective approach to impact women's underrepresentation in STEM; however, additional training and direct efforts to challenge well-intentioned but harmful behaviors may be needed to maximize their impact. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]