Inclusive research based on collaborative partnership with people with intellectual and developmental disabilities has the potential to lead to relevant and meaningful research outcomes. An inclusive research approach is necessary for research endeavors which strive to improve the lives of LGBTQ+ people with intellectual and developmental disabilities, who experience layered stigma due to complex interactions between their disabilities, gender and sexual identities, and other sociocultural identities. In this dissertation, I present three research articles about the Rainbow Inclusion Speaking Up (RISE Up) Project, an inclusive research project with and for LGBTQ+ adults with intellectual and developmental disabilities to promote gender and sexual self-determination. In chapter one, I define relevant terminology, justify the importance of inclusive research, and synthesize previous research on the experiences of LGBTQ+ people with intellectual and developmental disabilities. In chapter two, I organize prior scholarship about planning inclusive research into five components and describe how I planned The RISE Up Project according to these components. Then, in chapter three, I present a qualitative interview-based study on the barriers and facilitators to gender and sexual self-determination in the lives of LGBTQ+ adults with intellectual and developmental disabilities. In chapter four, I share practical lessons from The RISE Up Project on conducting gender and sexualities research consistent with core principles of community-based participatory research. Throughout this work, and in chapter five, I highlight implications for conducting meaningful inclusive research and for promoting gender and sexual self-determination for LGBTQ+ adults with intellectual and developmental disabilities. [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.]