Charles Francis Xavier, also known as Professor X, is a fictional character, a Marvel Comics superhero known as the leader and founder of the X-Men. Created by writer Stan Lee and artist/co-writer Jack Kirby, he first appeared in X-Men #1 (September 1963).

Throughout most of his comic book history, Xavier is paraplegic, although his body houses one of the world's most powerful mutant minds. A high-level telepath, Xavier can read, control and influence human minds. A scientific genius, he is also a leading authority on genetics, mutation, and psionic powers.

Xavier’s mission is to promote the peaceful affirmation of mutant rights, to mediate the co-existence of mutants and humans and to protect society from antagonistic mutants, including his old friend, the militant Magneto. To achieve this aim, he founded Xavier's School for Gifted Youngsters (later named the Xavier Institute) to teach mutants to explore and control their powers. Its first group of students was the original X-Men. Xavier's students consider him a visionary and often refer to their mission as "Xavier's dream", and is highly regarded by others in the Marvel universe, respected by various governments and trusted by several other superhero teams, including the Avengers and the Fantastic Four. However, he also has a manipulative streak which has resulted in several significant fallings-out with allies and students.

He also often acts as a public advocate for mutant rights and is the authority most of the Marvel superhero community turns to for advice on mutants. However, his status as a mutant himself and leader of the X-Men has only recently become public.

In the comics' history, the X-Men rarely operate without Xavier. He also appears in both X-Men animated series and in many video games, although usually as a non-playable character because he can't use his legs. Patrick Stewart plays him in the 2000s film series, as well as providing his voice in some of the X-Men videogames (including some not connected to the film series).

According to BusinessWeek, Charles Xavier is listed as one of the top ten most intelligent fictional characters in American comics.