Sexual minority adults report worse mental health than heterosexual peers, although few empirical studies are large enough to measure variation in these disparities by sexual orientation, age, ethnicity, and socioeconomic status (SES). We investigate chronic mental health problems among sexual minority adults. Sex-disaggregated logistic regressions examined associations between self-reported chronic mental health problems and sexual orientation, age, ethnicity, and SES in a 2015-2017 dataset from the nationally representative English General Practice Patient Survey data ( = 1,341,339). Bisexual adults, especially young bisexual females, reported the highest rates of chronic mental health problems. Sexual minority females 18-24 years of age had five times the odds of reporting chronic mental health problems of their heterosexual peers, with 32% of sexual minority females 18-24 years of age reporting the outcome. Sexual minority identity was also strongly associated with chronic mental health problems for adults who were White and lived in more affluent areas. The very high odds of chronic mental health problems among bisexual adults, especially younger bisexual females, may reflect simultaneous isolation from sexual minority and heterosexual communities. Elevated odds at younger ages may reflect disproportionate social media use and bullying. It is plausible that those who are subject to minority stress associated with SES and ethnicity may develop resilience strategies that they then apply to sexual minority stress. The results suggest that sexual minority identity is a source of minority stress, even for those who are affluent. Clinicians should be alert to the need to support the specific mental health concerns of their sexual minority patients.