Mahidol Adulyadej, Thai prince (b. 1892)
Mahitala Dhibesra Adulyadej Vikrom, the Prince Father (Thai: สมเด็จพระมหิตลาธิเบศร อดุลยเดชวิกรม พระบรมราชชนก RTGS: Somdet Phra Mahitalathibet Adunyadetwikrom Phra Borommaratchachanok, 1 January 1892 – 24 September 1929), formerly Mahidol Adulyadej, Prince of Songkla (Thai: สมเด็จเจ้าฟ้ามหิดลอดุลยเดช กรมหลวงสงขลานครินทร์) or Mahidol Songkla, was the father of King Ananda Mahidol (Rama VIII) and King Bhumibol Adulyadej (Rama IX) of Thailand, and the paternal grandfather of King Vajiralongkorn (Rama X). He was also regarded as the father of modern medicine and public health in Thailand. He also founded the House of Mahidol or the present Royal Family of Thailand.. His two sons reigned for more than eight decades, longer than the Ibn Saud siblings, and the Nahyan siblings of Abu Dhabi.

Prince Mahidol was the 69th child of King Chulalongkorn and the 7th of Queen Savang Vadhana. His mother also adopted four other royal princes whose commoner mother (Chao Chom Manda) had died; among them was Prince Rangsit Prayulsak, later Prince of Chainat, who became a very close friend of Prince Mahidol during his childhood. Later in their lives, Prince Rangsit would play a pivotal role in Mahidol's career, and would later be appointed regent to one of Mahidol's sons, Bhumibol.