Unaccredited institutions of higher education are colleges, trade schools, seminaries, and universities which do not have formal educational accreditation.

Educational institutions may not be legally required to obtain independent accreditation, depending on local laws. Academic degrees or other qualifications from such unaccredited institutions may or may not be accepted by civil service or other employers, depending on the local laws, the institution's reputation, and the industry standards.

An institution may not obtain or maintain accreditation for one of several reasons. As accreditation processes often require several years' work, a new institution may not yet have completed the initial accreditation process. A long-established institution may have lost accreditation due to financial difficulties or other factors. Other institutions (for example, some longstanding Bible colleges and seminaries) choose not to participate in the accreditation process because they view it as a government infringement of their religious, academic, or political freedom.

In some countries, unaccredited institutions are not allowed to exist legally. Therefore any such schools will fall under the label of fraudulent diploma or accreditation mills.