April 2023 marks 5 years since WHO announced its global campaign to combat ageism, defined as stereotyping, prejudice, and discrimination towards people on the basis of their age. Like other forms of discrimination, ageism has negative health consequences, and it can affect whether older adults receive appropriate health care. Ageism has particular relevance to cancer care, because most people with cancer are older adults, and cancer incidences are expected to increase globally as populations age.