An apostolic constitution (Latin: constitutio apostolica) is the most solemn form of legislation issued by the Pope.

By their nature, apostolic constitutions are addressed to the public. Generic constitutions use the title apostolic constitution and treat solemn matters of the church, such as the promulgation of laws or definitive teachings. The forms dogmatic constitution and pastoral constitution are titles sometimes used to be more descriptive as to the document's purpose.

Apostolic constitutions are issued as papal bulls because of their solemn, public form. Among types of papal legislation, apostolic letters issued motu proprio are next in solemnity.