Background: In Australia, the incidence of hepatitis C virus (HCV) infection has declined among gay and bisexual men (GBM) with HIV since 2015 and is low among GBM using HIV pre-exposure prophylaxis (PrEP). However, ongoing HCV testing, and treatment, is required to sustain HCV elimination. Annual HCV testing is recommended in Australia for all GBM with HIV and GBM using PrEP regardless of sexual or substance use behaviours. Bacterial sexually transmissible infections (STIs) are associated with similar behaviours as HCV among GBM, and therefore may be useful to guide more personcentered and tailored HCV testing. To examine this, we measured the association between STIs and HCV from 2016 to 2020. Methods: Data were from a national network of primary care and sexual health clinics participating in the Australian Collaboration for Coordinated Enhanced Sentinel Surveillance (ACCESS). GBM included had at least one HCV antibody negative test during the observation period and ≥1 subsequent HCV test. Discrete time modelling estimated the association between a syphilis, rectal chlamydia, and rectal gonorrhoea diagnosis in the preceding two years on incident HCV infection, reported as an adjusted hazard ratio (aHR). Analyses were stratified by GBM with HIV and GBM prescribed PrEP and adjusted for age and the number of each STI test undertaken. Results: Among 6,529 GBM with HIV, 92 had an incident HCV infection which was associated with a syphilis infection (aHR 1.99, 95%CI:1.11--3.56). Of 13,061 GBM prescribed PrEP, 48 had an incident HCV infection, which was associated with rectal chlamydia (aHR 2.73, 95%CI:1.40--5.30) and rectal gonorrhoea (aHR 2.58, 95%CI:1.30--5.13). Conclusion: HCV was associated with bacterial STIs among GBM with HIV and GBM using PrEP. These findings suggest that an STI diagnosis should prompt a conversation about HCV testing, and that more frequent HCV testing may be justified among GBM with STIs. [ABSTRACT FROM AUTHOR]