Health concordance–health similarity between intimate partners–is understudied among different-sex cohabiting, same-sex cohabiting, and same-sex married couples due to an overwhelming focus on different-sex married couples. I explore whether existing research and theory extends to health concordance among different-sex cohabiting and same-sex couples. Additionally, I examine health concordance as a site of population health disparities at the couple level. I use the 2008–2018 IPUMS National Health Interview Surveys to perform multinomial logistic regressions of poor-to-fair health and activity limitations concordance on union status, demographic similarity, and socioeconomic resources. Health concordance is common among all couples, characterizing at least 86% of each union status. Marital status differentiates concordance risk for different-sex couples, but not same-sex couples. Same-sex female couples face higher risks of health discordance and concordant disadvantaged health than many other couples, both of which represent major health disadvantages. Union status affects health concordance risk for couples in ways that cannot be easily reduced to marriage, gender, or sex composition. Negative health concordance, especially for same-sex female couples and different-sex cohabitors, warrants further attention as a site of health inequalities. Socioeconomic resources may play a major role in promoting positive health concordance among couples, which could inform policy levers to improve couple health. Health concordance is a site of health disparities because the risk of partners’ concordance in poor health varies considerably depending on union status.