Piero Giorgio Bordoni (Rome, 18 July 1915 – 19 September 2009) was an Italian physicist, who first measured the anelastic relaxation effect (dissipation of elastic energy and softening of the elastic modulus), named after him, due to the stress induced motion of dislocations in metals.[1] That experiment, together with a similar one by T.S. Kê,[2] opened the way to the study of the dynamics of dislocations in solids. Those were also the first experiments of anelasticity in solids, a branch of physics studying defects, excitations and phase transitions in condensed matter, first systematised by Clarence Zener.[3]