George Green was a pioneering 19th-century mathematical physicist, whose work influenced modern physics. He was by trade a miller, of scant formal education until most his finest work was complete. Then, at the age of 40, he went to Caius College, Cambridge, to read for a degree in mathematics. He was without public recognition during his lifetime, and it was Kelvin who saw the importance of his work and gave it wide publicity. Today, Green's function technique has been adapted to quantam mechanical problems in areas as diverse as nuclear physics, quantam electrodynamics and superconductivity. This biography's publication coincides with the bicentenary of Green's birth.