Globally, over one million people acquire curable sexually transmitted infections (STI) each day. Understanding how people think about STIs is key to building culturally appropriate STI prevention and treatment programs. We explored STI knowledge and perceptions in rural, southwestern Uganda to inform future interventions. From August 2020 to December 2020, we conducted individual in-depth interviews among adult men and women (≥18 years) with recent or current personal or partner pregnancy, a history of an STI diagnosis and treatment, and membership in an HIV-sero-different relationship. Interviews explored STI knowledge, perceptions, and barriers and facilitators to engaging in STI care. We used inductive and deductive approaches to generate a codebook guided by the healthcare literacy skills framework in a thematic analysis. Ten men with STI, five of their female partners, eighteen women with STI, and four of their male partners participated in individual in-depth interviews. The median age was 41 (range 27-50) for men and 29 (range 22-40) for women. Sixteen (43%) participants were with HIV. Significant themes include: 1) Participants obtained STI knowledge and information from the community (friends, family members, acquaintances) and medical professionals; 2) While participants knew STIs were transmitted sexually, they also believed transmission occurred via non-sexual mechanisms. 3) Participants associated different connotations and amounts of stigma with each STI, for example, participants reported that syphilis was passed down "genetically" from parent to child. 4) Participants reported uncertainty about whether STIs affected pregnancy outcomes and whether antenatal STI treatment was safe. The complicated nature of STIs has led to understandable confusion in settings without formal sexual healthcare education. Robust counseling and education prior to sexual debut will help allow men and women to understand the signs, symptoms, and treatments necessary for STI cure and to navigate often complicated and overburdened healthcare systems.