His Majesty King Bhumibol Adulyadej The Great was born at Mt. Auburn Hospital (formerly Cambridge Hospital), Cambridge, Massachusetts, United States of America on 5 December 1927, the youngest son of HRH Prince Mahidol of Songkla (son of King Rama V and Queen Savang Vadhana) and HRH Princess Srinagarindra.
His Majesty has an elder sister, HRH Princess Galyani Vadhana, born on 6 May 1923 in London, England, and an elder brother, King Ananda Mahidol, Rama VIII, born on 20 September, 1925 in Heidelberg, Germany.
In 1928, His Majesty accompanied his father, who graduated as a medical doctor (cum laude) from Harvard University, to Thailand and the family took up residence at Sapathum Palace. When the Prince Father passed away on 24 September 1929, the young prince was not quite two years old,
At the age of five, His Majesty attended kindergarten at Mater Dei School in Bangkok. The following year the Princess Mother took her three children to Lausanne, Switzerland, and the young prince continued his education at Miremont Elementary School where His Majesty studied French, German and English.
His Majesty attended high school at Ecole Nouvelle de la Suisse Romande at Chailly-sur Lausanne. After receiving the diplome de Bachelier es Lettres from Gymnase Classique Cantonal of Lausanne, His Majesty enrolled in Lausanne University, majoring in Science.
While in Switzerland, the prince returned to Thailand twice with his brother King Ananda Mahidol the first time in 1938, staying at Chitralada Villa and the second time in 1945, staying at the Baromphiman Mansion in the Grand Palace,
On 9 June 1946 King Ananda Mahidol passed away and His Majesty King Bhumibol Adulyadej The Great succeeded him as King Rama IX on the same day. His Majesty went back to Switzerland once again in August 1946 to resume his study at the same university, changing his major from Science to Law and Political Science.
While staying abroad, His Majesty met Mom Rajawongse Sirikit Kitiyakara, the daughter of HSH Prince Nakkhatra Mangala Kitiyakara, the Thai ambassador to France and Mom Luang Bua Kitiyakara. In July 1949 His Majesty and MR Sirikit became engaged.
On 25 March 1950 His Majesty and his fiancee returned to Thailand on board the liner Selandia to attend the cremation ceremony of King Ananda Mahidol. On 28 April Queen Savang Vadhana presided over the royal wedding ceremony between His Majesty and MR Sirikit at Sapathum Palace. On this occasion MR Sirikit was elevated to Queen Sirikit.
The coronation ceremony according to ancient tradition took place at the Baisan Thaksin Throne Hall in the Grand Palace on 5 May 1950. His Majesty assumed the name of Somdet Phra Paramindra Maha Bhumibol Adulyadej Mahitalathibet Ramathibodi Chakri Nantebodin Sayaminthrathirat Boromnatbophit and uttered his first decree:
We shall reign with righteousness for the benefits and happiness of the Siamese people.
On this occasion, Queen Sirikit was elevated to Her Majesty Queen Sirikit.
After the coronation the royal couple returned to Lausanne. There, Her Majesty gave birth to her first child, Princess Ubolratana, at Mon Choisis Hospital on 5 April 1951.
When the princess was seven months old, the royal family returned to Thailand where they stayed at Ambara Villa, Dusit Palace, since Chitralada Villa was under renovation to be used as their permanent residence. At Ambara Villa, Her Majesty gave birth to three more children:
- King Maha Vajiralongkorn Phra Vajiraklaochaoyuhua
- Her Royal Highness Princess Maha Chakri Sirindhorn
- Her Royal Highness Princess Chulabhorn Krom Phra Srisavangavadhana
His Majesty entered the monkhood on 22 October 1956 at the Chapel Royal of the Temple of the Emerald Buddha in the Grand Palace.
His Majesty stayed at Panya Mansion, Wat Bovomives for 15 days while in the monkhood, during which time Her Majesty the Queen was proclaimed Regent, a responsibility which she carried out so well that she was further elevated to Somdet Phra Borom Rachininat in the same year.
On 31 October 1957, a house-warming ceremony was held at the newly renovated and expanded Chitralada Villa. The royal family then moved from Ambara Villa to reside at Chitralada Villa to the present.