BACKGROUND: Sexual activity is important to the holistic health of older adults. However, the sexual lives of older adults are understudied. We aimed to investigate the prevalence and correlates of sexual activity and sexual satisfaction among older adults in China. METHODS: In this multi-centre cross-sectional study, individuals aged 50 years and older were recruited from four regions in China between June 2020 and December 2022. An investigator-administered questionnaire was completed to collect information on socio-demographics, health status (general health and specific health), and sexual health characteristics. Sexual activity (including vaginal, oral, or anal sex) in the past year was treated as sexually active. Sexual satisfaction was measured using a validated five-point Likert scale. Logistic regression was used to assess correlates of sexual activity and sexual satisfaction. FINDINGS: 3001 older adults (1182 women and 1819 men, mean age 60.3 ± 7.8 years) were recruited. Most participants were living in urban areas (1688, 56.2%), in a stable relationship (2531, 84.3%), and satisfied with life (2141, 71.3%). 46.8% of men and 40.7% of women were sexually active. Better self-reported general health status (good: aOR 0.53, 95% CI 0.34-0.82; fair: 0.47, 0.29-0.76; bad or very bad: 0.58, 0.35-0.96; versus very good), no difficulty walking upstairs (0.63, 0.41-0.97), diabetes (0.64, 0.42-0.98), and menopause (0.57, 0.36-0.92), were associated with sexual activity among women. Such an association was not found among men. Among sexually active participants, about three-quarters (men: 73.6%, women: 73.4%) were sexually satisfied. Self-reported general health status (men [good: 0.25, 0.12-0.53; fair: 0.17, 0.08-0.37; bad or very bad: 0.15, 0.06-0.34]; women [good: 0.27, 0.10-0.70; fair: 0.11, 0.04-0.30; bad or very bad: 0.11, 0.04-0.32]), life satisfaction (men: 1.73, 1.22-2.46; women: 2.23, 1.34-3.71) and talking about sexual preferences with a partner (men: 1.77, 1.23-2.56; women: 2.93, 1.69-5.09) were associated with sexual satisfaction. INTERPRETATION: Older adults who had better health status and talked easily with their partners about their sex life were more likely to report sexual satisfaction. For women, better self-reported general health status and lack of disability were associated with sexual activity. Further research should address measures that improve sexual satisfaction, especially among sexually active older adults. FUNDING: This study was supported by the Natural Science Foundation of China International/Regional Research Collaboration Project [72061137001] and the Economic and Social Research Council [ES/T014547/1].