Sir Peter Brian Medawar, Brezilyalı/Britanyalı biyolog. Graft reddi ve kazanılmış immün tolerans ile ilgili keşifleri organ nakli uygulamalarında önemli bir yer edinmiştir. 1960 yılında Nobel Fizyoloji veya Tıp Ödülü'ne Sir Frank Macfarlane Burnet ile birlikte layık görüldü.
a novice must stick it out until he discovers whether the rewards and compensations of a scientific life are for him commensurate with the disappointments and the toil; but if once a scientist experiences the exhilaration of discovery and the satisfaction of carrying through a really tricky experiment-once he has felt that deeper and more expansive feeling Freud has called the "oceanic feeling" that is the reward for any real advancement of the understanding-then he is hooked and no other kind of life will do.