A ring announcer is an in-ring (and sometimes on-camera) employee or contractor for a boxing, professional wrestling or mixed martial arts event or promotion, who introduces the competitors to the audience.
In boxing and mixed martial arts bouts, introductions occur after both fighters have entered the ring or cage.
In-ring introductions are sometimes used for title matches or other major bouts, to add a "big fight feel".
In professional wrestling, the announcement is usually performed outside the ring, and typically doesn't mention the time or method of victory unless it is from disqualification, submission, or knockout; however, as professional wrestling shows do incorporate an official timekeeper at ringside, much like boxing and MMA, some ring announcers may be informed of the time of the fall at the match's conclusion and will relay that information to the audience as well.
Even further to this, some professional wrestling matches will stipulate a time limit, within which a wrestler must win if they wish to avoid a time-limit draw.