Social isolation is a growing problem for the elderly. Social isolation can be either subjective or objective. Objective isolation is defined by the social connections a person has, consisting of regular interactions with friends, family members, colleagues, or acquaintances. Subjective isolation is the experience of isolation, including feelings of loneliness and can manifest regardless of quantity of social connections. After defining isolation, this chapter reviews the causes and consequences of social isolation, including physical and mental illness, suicide, and substance use. The chapter also details how technology might alleviate isolation. We provide a review of the prevalence of social isolation in elderly populations in North America, Europe, Japan, and South Africa. The chapter concludes by reviewing potential solutions for isolation (i.e., social prescribing and community engagement, youth mentorship, social media, nonhuman companionship, and resiliency).