Suppressive person, often abbreviated SP, is a term used in Scientology to describe the "antisocial personalities" who, according to Scientology's founder L. Ron Hubbard, make up about 2.5% of the population. A statement on a Church of Scientology website describes this group as including notorious historic figures such as Adolf Hitler.

The term is often applied to those whom the Church perceives as its enemies, such as those whose "disastrous" and "suppressive" acts are said to impede the progress of individual Scientologists or the Scientology movement.

One of the reasons Scientology doctrines portray suppressive persons as such a danger is that they are supposed to make people around them become potential trouble sources (abbreviated PTS). Scientology defines a PTS as "a person who is in some way connected to and being adversely affected by a suppressive person. Such a person is called a potential trouble source because he can be a lot of trouble to himself and to others." Hubbard suggested that the effects of suppressive persons is amplified to cause 20% of the population to be predisposed against Scientology.

As with most Scientology terminology, "suppressive person" was coined by L. Ron Hubbard. Ruth A. Tucker writes in her book Another Gospel: Cults, Alternative Religions, and the New Age Movement that the concept appears to have first been introduced into Scientology in the 1960s "as membership grew and as authoritarian control [by Hubbard] increased". Tucker notes that many of those who joined Scientology during this period were "well-educated people who prided themselves in independent thinking [and] struggled with the idea of allowing any other individual to completely dominate their opinions." Many of Hubbard's early writings on suppressive persons focus on their alleged responsibility for poor management within the Church of Scientology.

The church's official glossary defines a suppressive person as being:

a person who possesses a distinct set of characteristics and mental attitudes that cause him to suppress other people in his vicinity. This is the person whose behavior is calculated to be disastrous. Also called antisocial personality.

The church regards these "antisocial personalities" as being those "who possess characteristics and mental attitudes that cause them to violently oppose any betterment activity or group". This concern with "groups" continues in the official Scientology Handbook, which states the corollary: "The antisocial personality supports only destructive groups."

According to the Hubbard textbook Introduction to Scientology Ethics ("the Ethics book"), when an individual is found to be under the influence of a suppressive person, it is believed that this will affect their general well-being. An individual with an SP in their vicinity is likely to be under stress or frequently upset, and this would potentially jeopardize the stability of any treatment or education. Therefore, a parishioner who is found to have such suppressive connections is not permitted to participate in certain Scientology classes and counseling until the situation has been adequately resolved.