Social support, which is the perception or experience that one is cared for, esteemed, and part of a mutually supportive social network, has beneficial effects on mental and physical health. We review the psychobiological pathways whereby these effects may occur and detail the circumstances under which socially supportive efforts may misfire. Origins of social support include genetic factors and the early environment. We examine gender and cultural differences in how social support is experienced. Under some circumstances, providing social support confers the same benefits as receiving it. A myriad number of social support interventions, including those delivered via the internet, have been evaluated and have the potential to provide emotional and informational support to people who might otherwise lack social support.