Implementing a patient navigation intervention across a health system to improve outcomes for patients with opioid use disorder - Opioid agonist treatment (OAT) is protective against overdose, yet less than 20% of people with opioid use disorder (OUD) engage in such treatment. Hospital utilization is high among people with OUD and can be a ‘reachable moment’ to initiate OAT. However, most hospitals lack the capacity to follow up with patients after discharge. Patient navigator (PN) interventions following hospital discharge can help patients engage in OAT and navigate complex systems of care. However, challenges persist in implementing PN interventions on a wide scale, as they require coordination across organizations, data sharing, dedicated personnel, and resources. To bring these interventions to scale, strategies are needed to determine feasibility, reach, and sustainability. Testing innovative implementation strategies for PN interventions has the potential for significant impact, as it will demonstrate implementation success of an intervention that can address the opioid epidemic in real-world settings and close the research-to-practice translation gap. The proposed study is a type II hybrid implementation-effectiveness trial of Navigation Services To Avoid Rehospitalization (NavSTAR). Our research team showed in a single-site randomized trial with 400 participants that NavSTAR significantly improved OAT entry, reduced readmissions, and was highly cost-effective compared to treatment as usual. The present study will test an Implementation Facilitation (IF) strategy to provide training, resources, and performance feedback to implement NavSTAR in four hospitals in Philadelphia. We hypothesize that engaging stakeholders in an IF strategy will yield an implementation process that is feasible, acceptable, and effective in improving outcomes for patients with OUD. The R61 phase will conduct process mapping to identify existing hospital workflow and then refine an IF strategy through sequential pilot trials at 4 hospital sites. R61 milestones include the creation of an implementation toolkit and data sharing agreements. During the R33 phase, we will conduct a type II hybrid-implementation-effectiveness trial (N=720) of NavSTAR using a randomized stepped-wedge design.