Truancy is a term used to describe an intentional unauthorized absence from compulsory schooling. The term typically refers to absences caused by students on their own free will, and usually does not refer to legitimate "excused" absences, such as ones related to a medical condition. The exact meaning of the term itself is subject to differ from school to school, and is usually explicitly defined in the school's handbook of policies and procedures. Truancy is the term referring to an absence associated with the most student irresponsibility and results in the greatest consequences.

Beyond the effect missed schooling may have on a student's academic record, truancy may indicate more deeply embedded problems with the student, the education system, or both. Truancy is commonly associated with juvenile delinquency. In some schools, truancy may result in an ineligibility to graduate or to receive credit for class attended, until the time lost to truancy is made up through a combination of detention, fines, or summer school.

Several studies indicate a high correlation between chronic truancy and poverty. Truancy may also be prevalent in dysfunctional families or among children placed in the care of local authorities.

Truancy has numerous slang terms invented by students. In the UK, it is colloquially known as bunking off, bobbing, wagging, dogging (Scotland), skiving or Mitching. In Ireland, the terms going on the hop and going on the lang are common. In the US, common terms include "playing hooky", "jigging", "ditching", "skipping", "sluffing", "skidding", and "cutting" class.