Objective To investigate the quality of intimate relationships of bisexual, gay, lesbian, and heterosexual individuals in Australia and the United Kingdom. Background There is a shortage of research on the relationship quality of nonheterosexual individuals, and the majority of the available evidence comes from the United States. We add to existing knowledge by considering bisexual individuals; examining mixed-orientation couples; and using recent, large, and nationally representative cross-national data. Method Data from 25,348 individuals in the United Kingdom (Understanding Society study) and 9,206 individuals in Australia (Household, Income and Labour Dynamics in Australia Survey) were used to estimate regression models predicting relationship quality while adjusting for confounds. Results Relationship quality in same-sex couples was as high as in heterosexual couples in the United Kingdom, and higher in Australia. The lowest relationship quality in both countries was reported by bisexual individuals. Conclusion Our results provide robust evidence to combat deep-rooted and erroneous social perceptions of same-sex relationships being conflictual, unhappy, and dysfunctional. Implications Our findings support policies that seek to legalize same-sex marriage and parenting rights. They also highlight the need to give further attention to bisexual individuals as a distinct group because their outcomes are comparatively poor.