Monsignor (; Italian: monsignore [monsiɲˈɲoːre]) is an honorific form of address or title for certain male clergy members, usually members of the Roman Catholic Church. Monsignor is the apocopic form of the Italian monsignore, meaning "my lord". "Monsignor" can be abbreviated as Mons or Msgr. In some countries, the title "monsignor" is used as a form of address for bishops. However, in English-speaking countries, the title is dropped when a priest is appointed as bishop.

The title "monsignor" is a form of address, not an appointment (such as a bishop or cardinal). A priest cannot be "made a monsignor" or become "the monsignor of a parish". The title "Monsignor" is normally used by clergy who have received one of the three classes of papal honors:

• Protonotary apostolic (the highest honored class)
• Honorary prelate
• Chaplain of his holiness (the lowest honored class)

The pope bestows these papal honors upon clergy who:

• Have rendered a valuable service to the church
• Provide some special function in church governance
• Are members of bodies such as certain chapters

Clerics working in the Roman Curia and the Vatican diplomatic service are eligible for all three honors. Priests working in a diocese are only eligible for the "chaplain of his holiness" honor. Priests must be nominated by their bishop and must be at least 65 years old.