Background: The burden of HIV/AIDS continues to impact the health and wellbeing of people living with HIV (PLHIV) globally, and HIV prevalence rates remain disproportionately high in sub-Saharan Africa (SSA). HIV stigma, which can be examined through distinct mechanisms, is associated with less than favorable health outcomes and behaviors. Psychosocial factors and other forms of stigma can intersect with HIV stigma, concurrently contributing to HIV outcomes. Finally, how researchers measure and operationalize HIV stigma can significantly impact the way in which scientists view and discuss HIV stigma and its effects on health-related outcomes and behaviors. Objective: The overarching goal of the proposed dissertation is threefold: (i) examine how the co-occurrence of HIV- and mental health-related stigma is related to HIV testing behaviors, (ii) measure changes in HIV stigma immediately after diagnosis, and examine if disclosure, linkage to care, and other factors that may be associated with short term changes in HIV stigma after diagnosis, are associated with those changes, and (iii) assess psychometric properties of three discrete HIV stigma scales. Methods: This dissertation utilized data from the Providing Access to HIV Care (PATH)/Ekkubo Study. This is a cluster-randomized controlled trial, which compares the efficacy of an enhanced linkage to HIV care intervention versus the standard-of-care for individuals living in rural Uganda.(1) Aim one examined the co-occurrence of anticipated social HIV- and mental health-related stigma, among men and women reporting as HIV negative in the PATH/Ekkubo baseline dataset. Aim two made use of data collected at three time points among PATH/Ekkubo intervention participants: diagnosis (baseline), two-weeks post-diagnosis, and six-weeks post-diagnosis. Changes in anticipated, enacted, internalized, and overall HIV stigma were assessed statistically. Then, linkage to care and other psychosocial factors were explored as variables associated with statistically significant changes in HIV stigma. Finally, aim three utilized PATH/Ekkubo six-month follow-up data, collected from individuals who were newly diagnosed at baseline, and randomized into the control arm. Psychosocial properties were measured and examined for three distinct HIV stigma scales: anticipated, enacted, and internalized. Results: In aim one, the relationship between anticipated social HIV stigma and HIV testing behaviors was moderated by depression stigma for females, but not males. In aim two, both internalized and overall HIV stigma statistically significantly decreased in the six weeks post-initial HIV diagnosis among women, but not men. Further examination of psychosocial factors associated with these changes revealed that changes in both internalized and overall HIV stigma, over time, are moderated by disclosure status among women. In aim three, the three revised HIV stigma scales demonstrated good construct validity, strong internal reliability, and measured and performed similarly across genders. The revised enacted and internalized scales demonstrated strong external criterion validity. Conclusions: HIV stigma, an ever-evolving phenomenon, remains ubiquitous in areas with high HIV disease burden. Public health efforts must continue to find new ways in which HIV stigma is related to HIV health behaviors and outcomes, with special efforts made to modernize HIV stigma measurement tools.