In the Scientology religion, man is held to consist of three parts—thetan, mind and body. The thetan is the spiritual being. The thetan is the individual. One is a thetan who has a mind and who occupies a body.

The thetan is that which animates the body and uses the mind. One of the most basic tenets of Scientology is that man is an immortal spiritual being whose experience extends well beyond a single lifetime and whose capabilities are unlimited, even if not presently realized.

The term is taken from the Greek letter theta for thought or life or the spirit. It is used to avoid confusion with previous concepts of the soul.