Bragg's father was a merchant seaman turned farmer. William Henry Bragg was born in Westwood in England and educated at a variety of schools before going as a scholar to Cambridge University. He graduated in 1884 and after a year's research under J. J. Thomson took the chair of mathematics and physics at the University of Adelaide, Australia, in 1886. He returned to England as professor of physics at Leeds University in 1909, moving from there to University College, London, in 1915.

In Australia, Bragg concentrated on lecturing and started original research late in life (in 1904). He first worked on alpha radiation, investigating the range of the particles. Later he turned his attention to x-rays, originally believing (in opposition to Charles Barkla) that they were neutral particles. With the observation of x-ray diffraction by Max von Laue, he accepted that the x-rays were waves and constructed (1915) the first x-ray spectrometer to measure the wavelengths of x-rays. Much of his work was on x-ray crystallography, in collaboration with his son, William Lawrence Bragg. They shared the Nobel Prize for physics in 1915.

During the war Bragg worked on the development of hydrophones for the admiralty. In some ways his most significant work was done at the Royal Institution, London, where he was director from 1923. Under James Dewar's directorship the research functions of the Royal Institution had virtually disappeared. Bragg recruited several young and brilliant crystallographers who shared with him a commitment to applying the new technique to the analysis of organic compounds. There was no reason to suppose there was much chance of success but as early as the 1920s Bragg was planning to investigate biological molecules with x-rays. His first attempts were made on anthracene and naphthalene in 1921.