Bertram Sidney Thomas (13 June 1892 – 27 December 1950) was an English civil servant who is the first documented Westerner to cross the Rub' al Khali (Empty Quarter). He was also a scientist who practiced craniofacial anthropometry,
He was born in Pill near Bristol and educated at Trinity College, Cambridge. After working for the Civil Service in the General Post Office, he served in Belgium during World War I before being posted to the Somerset Light Infantry in Mesopotamia (now Iraq) between 1916 and 1918. He worked as an Assistant Political Officer in this country from 1918 to 1922, and Assistant British Representative in Transjordan (now Jordan), from 1922 to 1924. He was appointed as Finance Minister and Wazir to the Sultan of Muscat and Oman (now Oman), a post he held from 1925 to 1932. In this capacity, he undertook a number of expeditions into the desert, and became the first European to cross the Rub' Al Khali from 1930 and 1931, a journey he described in Arabia Felix (1932), in which he described this desert’s animals, inhabitants, and culture.
Besides Arabia Felix, he wrote several other books, including The Arabs: The Epic Life Story of a People Who Have Left Their Deep Impress on the World (London: T. Butterworth, 1930; Garden City, New York: Doubleday, Doran and Co., Inc., 1937).
A recent film called 'Crossing the Empty Quarter' was created by the Anglo-Oman Society's Chairman, Richard Muir — the ex-Ambassador to Oman — from footage taken by Thomas on his journey, and photographs from the Library of the Oriental Institute in Cambridge.
He returned to England and died in the house in which he was born (or possibly in Cairo), in 1950.
- Explore Saudi Arabia. "Bertram Thomas 1892-1950." 26 September 2007
- Ure, John. "Thomas, Bertram Sidney". Oxford Dictionary of National Biography. Retrieved 2008-08-07.
- "BT Bertram Sidney Thomas (1892-1950), Explorer". Faculty of Asian & Middle Eastern Studies. University of Cambridge. Retrieved 2008-08-07.
- "Archive collections in the oriental studies faculty library". Canmbridge University libraries information bulletin. University of Cambridge. 2003. Archived from the original on 2008-05-21. Retrieved 2008-08-07.
- "The Forgotten Explorer" (PDF). Broad view Newsletter. University of East Anglia. March 2004. Retrieved 2008-08-07.