produced the most mentions of Truvada. We developed a codebook based on themes identified in a subset of posts and thematically coded all posts based on the primary purpose expressed in post titles and body. All data are descriptive. Results We identified 1,163 PrEP-related posts in total. There was a 23.3 fold increase in posts per year from 2014 (first year of posts) to 2019. The proportion of posters self-identifying as not on PrEP (26.8%) and on PrEP (30.3%) were similar. Incidental mentions of PrEP (54.5%), access challenges (19.1%), information seeking (17.5%), and cultural effects (16.3%) were the most common themes. 19.2% of posts involved assessment of risk following a sexual encounter. The topics mentioned least frequently, each with <5.5% of posts, focused on active promotion of PrEP use, stigma, and usage questions. Discussion Reddit is a useful way of documenting user-initiated interest in discussion of PrEP. The frequent incidental mention of PrEP reflects the normalization and perceived importance of PrEP. Reddit may be less useful for gaining insight into issues like usage and side effects.