People who identify as lesbian, gay, bisexual, transgender, and queer and other people who are sexual and gender minorities (denoted by the umbrella term LGBTQ+) experience more physical and mental health problems than cisgender or heterosexual people, in part due to excess stress of experiencing stigma. Although it is important to document negative events in LGBTQ+ people's lives, it is also necessary to identify conditions that provide LGBTQ+ people with the opportunity to thrive. One key psychological factor that can promote prosperity and lessen LGBTQ+ people's disparate health problems is a sense of belonging. In this Review, we summarize factors identified in the psychological science, public health, and public policy literatures that influence LGBTQ+ people's belonging. We use a social ecological model to describe factors that enhance and detract from belonging at the individual, interpersonal, community, and societal levels. Our multi-pronged approach encourages the flourishing ofLGBTQ+ people as individuals while addressing structural forces that shape their psychosocial well-being. This Review is a resource for researchers, health practitioners, and policymakers who seek to understand diverse factors of belonging based on sexual orientation and gender diversity.