Common examples of collectivism are racism and sexism.
Many political systems are based on collectivism. Communism regards people with reference to their supposed economic class. Nationalism regards people with reference to their nationality. Typically, political collectivists hold that different groups have competing interests, and that the individual's interests are in fact tied up with the interests of their group. This line of reasoning often leads to the suppression of individual rights, which are sacrificed for the alleged good of the group.