Solemn Mass (Latin: missa solemnis) is the full ceremonial form of the Tridentine Mass, celebrated by a priest with a deacon and a subdeacon, requiring most of the parts of the Mass to be sung, and the use of incense. It is also called High Mass or Solemn High Mass. However, in the United States the term "High Mass" is also used to describe the less elaborate Missa Cantata, which lacks deacon and subdeacon and some of the ceremonies connected with them.
These terms distinguish the form in question from that of Low Mass and Missa Cantata. The parts assigned to the deacon and subdeacon are often done by priests in vestments proper to those roles. A Solemn Mass celebrated by a bishop has its own particular ceremonies and is referred to as a Solemn Pontifical Mass.