Space Captain Greg Martin is a character from Thunderbirds Are Go. He served as the second-in-command of the Zero X flight crew during both its first and second flights.
Born in Hawaii, Martin used to work for Paul Travers as a junior flight controller. Following Travers' recommendation that the former join the Zero X training programme, Martin partook in early ground tests, following which he was unanimously selected as the second-in-command.

Greg Martin at the controls of Zero X (far left)
Trivia[]
- Greg Martin attended the meeting at the Space Exploration Center that was held after the first Zero-X flight. In the closing scene at The Swinging Star, he can be seen standing behind Jeff Tracy, joining in the toast.
- The same puppet appeared in Give or Take a Million as a guest at Harman's Christmas party. In Thunderbird 6, it played Lane (Imposter).