Significant improvements in intergroup relations during the past century have been spurred by heightened awareness of the problem of prejudice and its inherent injustice, legal prohibitions against discrimination, changing norms, and individuals' adoption of less prejudiced personal attitudes. Nonetheless, an undercurrent of internalized bias remains for many people. Individuals who may not outwardly express traditional forms of prejudice may harbor internal prejudices. Theories of modern prejudice seek to provide a psychological account of this incongruity. This entry reviews the historical context of prejudice, discusses a number of forms of modern prejudice, and looks at tools for detecting these less overt attitudes.