Marital persistence in the face of chronic dysfunction has long been interpreted through cultural, religious, and socioeconomic lenses as an expression of commitment and moral fortitude. However, emerging psychological and sociological discourse challenges this normative framing by foregrounding the cumulative psychological toll that such persistence exacts on individuals—particularly women—in structurally unequal union contexts. This study examined the psychosocial, economic, and structural determinants of dysfunctional marital persistence among married adults in Uganda, operationalising a newly conceptualised construct termed the Marital Erosion Index (MEI) to capture the latent transition from voluntary commitment to involuntary endurance. Drawing on cross-sectional survey data from 400 purposively and systematically sampled respondents across urban and peri-urban settings in Kampala, the study employed univariate descriptive statistics, Pearson bivariate correlations, multiple linear regression, and structural equation modelling (SEM) to test hypothesised relationships among emotional exhaustion, fear of social stigma, financial dependency, perceived social support, and marital erosion. Findings revealed that emotional exhaustion (β = .44), fear of social stigma (β = .31), and financial dependency (β = .26) were the strongest positive predictors of marital erosion, while perceived social support (β = -.22) exerted a significant protective effect. The SEM model demonstrated excellent fit (CFI = 0.967; RMSEA = 0.048) and confirmed that the MEI mediated the relationship between psychosocial stressors and dysfunctional persistence (β = .68, p < .001). The study concludes that marital persistence in dysfunctional unions is not a unidimensional moral stance but a structurally compelled behavioural outcome. Recommendations are advanced for policy reform, counselling interventions, and social safety net programmes targeting women trapped in erosive marital arrangements.