Born in Lee, South London, Bagnold was educated at Charterhouse School and the Royal Military Academy, Woolwich. He was commissioned into the Royal Engineers in 1915 and served in France during World War I. After the war, he was seconded to the Egyptian Army and served in Egypt and Sudan. In 1931, he published The Physics of Blown Sand and Desert Dunes, which became a classic work in the field of desert geomorphology.
During World War II, Bagnold served in North Africa and Italy, and was awarded the Distinguished Service Order and the Order of the British Empire. He was also elected a Fellow of the Royal Society in 1941.
After the war, Bagnold returned to Egypt and continued his research on desert dunes. He also wrote a number of books on his experiences in the desert, including Libyan Sands (1935), The Nature of Desert Warfare (1941), and A Pilgrimage to Mecca (1933).
Bagnold died in Sevenoaks, Kent, in 1990 at the age of 93. He is considered one of the most influential desert geomorphologists of the 20th century.
In addition to his work on desert dunes, Bagnold also made contributions to the fields of soil mechanics, fluid mechanics, and military engineering. He was a prolific author and lecturer, and his work has had a lasting impact on the study of deserts and the development of military tactics.