Charles William "Bill" Mumy, Jr. (; born February 1, 1954), is an American actor, musician, pitchman, instrumentalist, voice actor, and a figure in the science-fiction community. He came to prominence in the 1960s as a child actor, when he was credited as Billy Mumy. His most notable role was in the 1960s CBS sci-fi television series Lost in Space, where he played Will Robinson, the youngest of three children in the Robinson family.