- Full name: William Edward Robinson
- Birth date: February 1, 1987
- Birth place: Santa Fe, New Mexico, USA
- Height (at launch): 4 feet, 3 inches
- Weight (at launch): 60 pounds
- Eyes: Hazel… Hair: Red
- Hobbies/interests: Geology, electronics, playing the guitar and singing.
The original pilot described Will as having recently graduated from the Camden Canyon School of Science at the age of 9 with the highest average in the school's history.
By the age of 5, people were already calling Will Robinson "the little genius." At the age of 6 (when he was already in the third grade), he dismantled the family's VCR, then put it back together again in perfect working order—much to his family's amazement. His I.Q. at the time of the Jupiter 2's liftoff was 182, and he had just graduated from the Santa Fe High School of Science.
On Earth, Will's extraordinary intelligence made him something of a misfit. Neither children his own age nor the older students with whom he attended school understood him very well. He often tried to take on adult responsibilities, but adults had trouble taking him seriously.
Will's attempts to make adult decisions were still creating problems after leaving Earth, as he often endangered both himself and his family by going off on his own without John or Maureen's permission. On the other hand, his intelligence and common sense saved the space pioneers and Dr. Smith, with whom he has developed a deep friendship, on many occasions.
Among Will's chief characteristics is his intense curiosity. This often gets him into trouble, as when he set off on his own to explore a seemingly derelict alien ship the Robinsons encountered soon after the family became lost in space. He is also intensely loyal, even to those (like Dr. Smith) who don't always deserve it. Will is very devoted to the Robinsons' B-9 environmental control robot, even though it once tried to kill him, and has used his skill with electronics to keep the Robot functioning at a high level. On a personal level, Will is sometimes sarcastic, but he is always polite. Perhaps because he is the youngest member of the crew, Will seems to have adapted better to the uncertainties of life in space better than anyone else on the Jupiter 2. Will's constant companions are Dr. Smith and the Robot. Will says that he and the Robot are like brothers.