Colonel Jack O'Neill is a fictional character from the science fiction television series Stargate SG-1. He is portrayed by actor Richard Dean Anderson and serves as the leader of a military team that explores other planets through a device called the Stargate. O'Neill is known for his dry humor, tactical skills, and strong sense of duty. Throughout the series, O'Neill faces various alien threats and challenges, often working alongside a diverse team that includes characters like Dr. Daniel Jackson, Teal'c, and Major Samantha Carter. His character evolves over the seasons, showcasing his leadership qualities and personal growth in the face of intergalactic adventures.