Mahidol Adulyadej, Prince of Songkla (Thai: สมเด็จเจ้าฟ้ามหิดลอดุลยเดช กรมหลวงสงขลานครินทร์) or Mahidol Adulyadej the Prince Father (Thai: สมเด็จพระมหิตลาธิเบศร อดุลยเดชวิกรม อดุลยเดชวิกรม พระบรมราชชนก rtgs: Somdet Phra Mahitalathibet Adunyadetwikrom Phra Borommaratchachanok, 1 January 1892 – 24 September 1929) or Mahidol Songkla was the father of King Ananda Mahidol (Rama VIII) and King Bhumibol Adulyadej (Rama IX) of Thailand. He was also regarded as the father of modern medicine and public health of Thailand. He also founded the House of Mahidol or the present Royal Family of Thailand.

Prince Mahidol was the 69th child of King Chulalongkorn and the 7th of Queen Savang Vadhana. His mother also adopted four other princes whose commoner mothers (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 son Bhumibol.

Mahidol usually refers to Prince Mahidol Adulyadej of Songkla, father of King Bhumibol Adulyadej of Thailand. The name may also refer to: