The Honor System is a philosophical way of running a variety of endeavors based on trust and honor. Something that operates under the rule of the "honor system" is usually something that does not have strictly enforced rules behind its functioning. In the UK, it would more often be called a "trust system", and should not be confused with the British honours system.

A person engaged in a honor system has strong negative connotations associated with breaking or going against it. The negitives may include things like community shame, loss of stature, or in extreme situations, banishment.

In some places, for example, public transportation such as trains operate on an honor system. The local government may find it impractical or overly expensive to install ticket-checking turnstiles at every station, and instead rely on casual human surveillance to check if all train riders posess tickets. In such a system one could thus ride the train without paying, and simply hope he would be lucky enough to avoid a random ticket check during his trip. Though unethical, such behavior is impossible for an honor system to prevent.