Lieutenant Commander William McCoy is a fictional character from the Star Trek franchise, known for his role as the chief medical officer aboard the USS Enterprise. He is often referred to simply as "Bones" and is characterized by his gruff demeanor and deep commitment to his patients. McCoy frequently clashes with the ship's science officer, Spock, due to their differing philosophies on life and medicine. McCoy's character is portrayed by actor DeForest Kelley in the original series and subsequent films. He is known for his catchphrase, "I'm a doctor, not a..." which he uses to humorously express his frustration with being asked to perform tasks outside his medical expertise. His character embodies the ethical dilemmas faced by medical professionals in space exploration.