Wherever there is science, there are scientists; and wherever there are scientists there is rivalry. Rivalry is a key feature of scientific endeavour. This text examines eight instances in the history of science and technology that changed the world, in all of which the stress of rivalry played a pivotal role. The driving force of rivalry takes many forms, whether between individual scientists, groups of scientists, institutions or among the international scientific community. The stories of Newton and Leibniz, Lavoisier and Priestley, Darwin and Wallace, Edison and Tesla, the race for the atom bomb, Crick and Watson, the space race, and the feuds between Bill Gates and Larry Ellison illustrate the varying forms rivalry can take.