Truancy or skipping class/school is any intentional, unjustified, unauthorized, or illegal absence from compulsory education. It is a deliberate absence by a student's own free will (though sometimes adults or parents will allow and/or ignore it) and usually does not refer to legitimate excused absences, such as ones related to medical conditions. Truancy is usually explicitly defined in the school's handbook of policies and procedures. Attending school but not going to class is called internal truancy. Some children whose parents claim to homeschool have also been found truant in the United States. In some schools, truancy may result in not being able to graduate or to receive credit for classes attended, until the time lost to truancy is made up through a combination of detention, fines, or summer school.

Truancy is a frequent subject of popular culture. Ferris Bueller's Day Off is about the title character's (played by Matthew Broderick) day of truancy in Chicago with his girlfriend and best friend. Truancy is also the title of a 2008 novel about a student uprising against a dictatorial educational system. There are experiences that show that thanks to the incorporation of Successful Educational Actions (SEAs) in schools with high absenteeism they have managed to reduce truancy and thus contribute to the improvement of academic success.

The term truant can also be used to describe a child that avoids duty, or is unruly, although this use is uncommon.