Ramsay, Sir William (1852-1916), a British chemist. Ramsay discovered the elements argon (1894, with Lord Rayleigh) and neon, krypton, and xenon (1898, with M. W. Travers). He was first to isolate helium (1895) and radon (1908), and discovered that helium is continuously produced by the disintegration of radium. Ramsay was awarded the 1904 Nobel Prize for chemistry.

Ramsay was born in Glasgow, and studied there and in Germany. He taught at University College, Bristol, 1880-87, and University College, London, 1887-1913. He was knighted in 1902.