The term 'marriageability' is used frequently in child marriage literature but is rarely defined. We propose a conceptual framework to define marriageability and use qualitative case studies to illustrate how ideas about marriageability contribute to child marriage. Pressure to capitalize on a girl's marriageability before it declines in order to secure the 'best' partner may explain why child marriage persists. We find that marriageability involves both eligibility-or perceived readiness for marriage-as well as desirability or 'value' on the marriage market. We propose that understanding marriageability in context, particularly in countries with limited evidence on interventions to address child marriage, is essential for suggesting ways interventions may critically examine notions of marriageability and disrupt pathways to child marriage.