This study will examine the effectiveness of opioid use disorder (OUD) treatment linkage strategies for patients seen at sexual health clinics. This 3-arm RCT will compare Usual Care vs. Patient Navigation vs. Patient Navigation + Buprenorphine Initiation (UC vs. PN vs. PN+BUP). Description: This study, entitled Opioid Use Disorder Treatment Linkage at Sexual Health Clinics using Buprenorphine (OUTLAST-B), will examine opioid use disorder (OUD) treatment linkage strategies for people receiving sexual health services from public clinics and health departments. This three-arm, parallel randomized clinical trial (RCT) will compare Usual Care (UC), vs. referral via Patient Navigation (PN), vs. Patient Navigation with buprenorphine initiation (PN+BUP). The study will examine participant outcomes in the domains of: (1) OUD treatment entry and retention, (2) Opioid use and related problems (including fatal and non-fatal overdose), and (3) HIV/STD-related outcomes.