Gaius Baltar is the brilliant Colonial scientist who unintentionally gives the Cylons the keys to the Command Navigation Program (CNP), ensuring the success of their devastating attack on Colonial space. Baltar carried on a two-year affair with a woman he believed to be a corporate spy for a private firm, granting her access to his nation’s most vital defense technology. When the Cylons launched their attack, featuring a computer virus that annihilated his programs, Baltar realized he had been engaged in an affair with a Cylon spy in humanoid form.

Baltar is plagued by guilt and shame, driven by a fierce will to live. He is the ultimate survivor with an uncanny ability (or destiny) to land on his feet, regardless of the choices he makes. Number 6, (the Cylon who seduced him) now appears to him in uncontrollable visions, taunting him, guiding him, manipulating him. His visions and insight result in him becoming a revered religious figure for the remnants of humanity. Though not without minor flaws, Dr. Baltar has acted selflessly on numerous occasions, and has saved the fleet multiple times. He's portrayed by James Callis in the Battlestar Galactica TV series.