Epigenetics refers to phenotypic changes caused by mechanisms that are unrelated to changes in the underlying DNA sequence, most notably chromatin remodeling driven by histone modifications, and DNA methylation. Such variation is transmitted by cell division, but generally not passed on through the germ line. An increasing body of evidence supports a role for epigenetic changes in the etiology of aging and its associated disease sequelae. Here, we review the role of epigenetics in aging and longevity with a focus on DNA methylation. Increased understanding of those aging-related processes that are driven by epigenetic mechanisms will allow for the development of novel epigenetic-based diagnostic, preventive, and therapeutic strategies for age-related diseases.