This work introduces the readers to the System Justification Theory, which presents a new insight into the existing knowledge on intergroup relationships. While the System Justification Theory complements the already accepted theories such as the Social Identity Theory or the Social Dominance Theory, it also opposes and argues with them and proposes a research forcing us to think about intergroup relationships from a different point of view. The manuscript focuses at first on the definition of basic terms and the Theory’s hypot­heses; then it explains psychological mechanisms of justification of “the unfair” system; discusses the position and inner conflicts of disadvantage groups; focuses on the preference of the non-member group and on stereotypes as one of the principal forms of rationalization of social position; and finally, it mentions the discussion with other theories.