Sidney George Francis Guy Skinner (1912 – 11 October 1941) was a friend, collaborator, and lover of the Austrian philosopher Ludwig Wittgenstein.

Meanwhile, his sister Priscilla continued her mathematical career, winning a Fellowship and, during the Second World War, working as a mathematician at the Royal Aircraft Establishment.

(Priscilla's daughter is chemist Ruth Lynden-Bell) He attempted to join the International Brigade during the Spanish Civil War but was rejected on medical grounds.

Skinner died from polio, following an air raid in Cambridge in October 1941, having been neglected during the rush to treat victims of the bombing.

[1] Despite the weakening of their relationship, Wittgenstein was apparently traumatised by Skinner's death, resulting in the loss for 7 years of the work they were engaged in together, the 'Pink Book'.