In this study, we investigate how loneliness develops over the marital dissolution process in older age (i.e., transition at or after age 50) while paying close attention to heterogeneities by the dissolution pathway—widowhood and separation—and gender. Using data from over 8,000 Household, Income and Labour Dynamics in Australia (HILDA) survey respondents, we assess the association of interest using fixed effects regressions. Findings indicate that loneliness increased in the year before widowhood or separation among both women and men. Levels spiked in the year of dissolution, particularly for widowhood, but less for separation. Widowed men were substantially more affected than widowed women, while gender differences were negligible for separation. While loneliness levels gradually declined, widowed men remained vulnerable for remarkably long periods. Such chronic loneliness might be linked to other health disadvantages. These findings highlight the importance of long-term and gender-specific approaches to social support and integration after marital dissolution.