Outreach is the activity of providing services to any population that might not otherwise have access to those services. A key component of outreach is that the group providing it is not stationary, but mobile; in other words, it involves meeting someone in need of an outreach service at the location where they are. In addition to delivering services, outreach has an educational role, raising the awareness of existing services. It includes identification of under-served populations and service referral.

Outreach is often meant to fill in the gap in the services provided by mainstream (often governmental) services, and is often carried out by non-profit, nongovernmental organizations. This is a major element differentiating outreach from public relations. Compared with staff providing traditional services, outreach staff can potentially be less qualified but more highly motivated.