An apostolic constitution () is the most solemn form of legislation issued by the Pope. It is one of several types of papal bull that can be issued from the Vatican.
This high-level document normally deals with matters related to the governance and structure of the Church such as confirming laws, regulations, or institutions within the Church.
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. Another example is Pope Pius XII’s Munificentissimus Deus, the dogma of the Blessed Virgin Mary’s Assumption.
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.
Pope Francis issued 20 apostolic constitutions during his time as pontiff.