Compared to a large body of work on how gender may affect young women’s vulnerability to HIV, we know little about how masculine ideals and practices relating to marriage and fertility desires shape young men’s HIV risk. Using life-history interview data with 30 HIV-positive and HIV-negative young men aged 15–24 years, this analysis offers an in-depth perspective on young men’s transition through adolescence, the desire for fatherhood and experience of sexual partnerships in rural Uganda. Young men consistently reported the desire for fatherhood as a cornerstone of masculinity and transition to adulthood. Ideally young men wanted children within socially sanctioned unions. Yet, most young men were unable to realise their marital intentions. Gendered expectations to be economic providers combined with structural constraints, such as limited access to educational and income-generating opportunities, led some young men to engage in a variety of HIV-risk behaviours. Multiple partnerships and limited condom use were at times an attempt by some young men to attain some part of their aspirations related to fatherhood and marriage. Our findings suggest that young men possess relationship and parenthood aspirations that—in an environment of economic scarcity—may influence HIV-related risk.