Undiagnosed Children’s Awareness Day, also known as Undiagnosed Children’s Day, is observed worldwide every last Friday of April. This day was created to highlight the challenges faced by thousands of children living with undiagnosed or rare genetic conditions, often referred to as syndromes without a name (SWAN). These conditions can lead to significant physical, mental, emotional, cognitive, or behavioral challenges, yet remain difficult to diagnose due to their atypical symptoms or rarity. Families of these children often experience frustration with healthcare systems, feelings of isolation, and a complex web of medical appointments. National SWAN organizations in Australia, the United Kingdom, and the United States promote this awareness day, providing support and information to affected families. Participation can include learning about SWAN, volunteering for organizations, organizing fundraisers, and sharing information on social media using specific hashtags.