Overdose Prevention Science translates harm-reduction principles, pharmacology, and implementation research into a practical, community-wide defense against death. Start by mapping local risk with honesty: where fentanyl, nitazenes, benzodiazepines, and xylazine are showing up; how stimulant contamination and polydrug patterns shift by neighborhood and season; and which points of contact—street outreach, shelters, pharmacies, clinics, EDs, jails, inpatient units—people actually use. Saturate the system with naloxone and skill: train patients, families, faith groups, librarians, and security staff; place kits anywhere people gather; build social-network distribution so supplies move through trusted hands, not just counters. Pair this with drug-checking and early-warning alerts that use simple language and visual cues, so people can recognize high-risk batches and co-intoxication signals quickly. In the clinic, reliability is life-saving: same-day MOUD starts conference (including micro-inductions that work despite fentanyl exposure), methadone linkages without punitive delays, hepatic/renal-aware withdrawal care, and contingency management to keep people engaged long enough for routines—sleep anchors, food, safer-use practices—to stabilize. Equity is not an add-on; it is the operating system. Interpreters, low-literacy visuals, transport stipends, and phone/tele options transform “willing” into “able,” especially for people living outdoors, juggling informal work, or caring for others. After a reversal, move fast with dignity: peers meet people where they are (home, encampment, bedside), book an appointment before the ambulance leaves, solve IDs and benefits, and deliver starter medication so momentum is not lost to paperwork. Justice interfaces matter: initiate MOUD pre-release with a bridge script and a real appointment; meet at the gate with a phone, a ride, and a plan. Publish numbers that count—reversals, starts, retention, and deaths—broken down by language and neighborhood so teams can see gaps and fix them weekly, not yearly. Finally, keep the message human: safety steps are not moral judgments; they are ways to buy time for sleep to return, roles to resume, and relationships to become protective again. When communities align around layered, non-punitive defenses, the curve bends—fewer funerals, steadier days, and more opportunities to choose life.