Robert Neil Butler (1927--2010) was a scholar, psychiatrist, and Pulitzer Prize--winning author who revolutionized the way the world thinks about aging and the elderly. One of the first psychiatrists to engage with older men and women outside of institutional settings, Butler coined the term "ageism" to draw attention to discrimination against older adults and spent a lifetime working to improve their status, medical treatment, and care. Early in his career, Butler seized on the positive features of late-life development -- aspects he documented in his pathbreaking research on "healthy aging" at the National Institutes of Health and in private practice. He set the nation's age-based health care agenda and research priorities as founding director of the National Institute on Aging and by creating the first interprofessional, interdisciplinary department of geriatrics at New York City's Mount Sinai Hospital. In the final two decades of his career, Butler created a global alliance of scientists, educators, practitioners, politicians, journalists, and advocates through the International Longevity Center. A scholar who knew Butler personally and professionally, W. Andrew Achenbaum follows this pioneer's significant contributions to the concept of healthy aging and the notion that aging is not synonymous with physical and mental decline. Emphasizing the progressive aspects of Butler's approach and insight, Achenbaum affirms the ongoing relevance of his work to gerontology, geriatrics, medicine, social work, and other related fields.