This paper examines how older adults living in rural Malawi explain and understand their sex lives. We present sex in this setting as a field in which broader understandings of ageing, aged identities, and conceptions of person- or adulthood in older age are played out and constructed. Qualitative data were collected from men (N=20) and women (N=23) aged 50 to around 90 using in-depth multiple dependent interviews (N=135) between 2008 and 2010. The giving and receipt of sexual pleasure was considered natural and God-given. Primarily understood as a matter of ‘power’, sex was on the one hand, beneficial to older bodies, but on the other, not accessible to such bodies. Declining sexual frequency was associated with declining desire for sex, or frustration stemming from continued desire for sex. These discourses emerged from the way the ageing body was constructed as a weakened body, incompatible with understandings of adulthood based on physical productivity. Older men and women used sex to discursively respond to these challenges to their adulthood in two ways. Firstly, sex was used to confirm strength, physical productivity, and therefore, identity as an ‘adult’. Secondly, adulthood itself was redefined as being based on moral, rather than physical productivity, and refraining from sex was used to demonstrate wisdom, self-control and therefore their ‘adult’ identity. Our results provide in-depth understanding of the ways constructions of ageing and sex can influence complex experiences of marital and non-marital sex in older age. We contribute to debates on sexuality in the gerontological literature by moving discussion beyond the presentation of continued sexuality as somehow exceptional or an indicator of successful ageing. Finally, in a setting of considerable HIV prevalence at older ages, our results challenge a preoccupation with fertility and chronological age in the collection of sexual health data in Africa.