Definition: Referee

An official named by the Committee to decide questions of fact and apply the Rules.

In match play, a referee's duties and authority depend on their assigned role:

When a referee is assigned to one match for the entire round, the referee is responsible for acting on any breach of the Rules that they see or are told about (see Rule 20.1b(1)).
When a referee is assigned to multiple matches or to certain holes or sections of the course, they have no authority to become involved in a match unless:

A player in a match asks for help with the Rules or requests a ruling (see Rule 20.1b(2)).
A player or players in a match may be in breach of Rule 1.2 (Standards of Player Conduct), Rule 1.3b(1) (Two or More Players Agree to Ignore any Rule or Penalty they Know Applies), Rule 5.6a. Unreasonable Delay of Play (Unreasonable Delay of Play) or Rule 5.6b (Prompt Pace of Play).
A player arrives late to their starting point (see Rule 5.3), or
A player’s search for a ball reaches three minutes (see Rule 5.6a and definition of lost).

In stroke play, a referee is responsible for acting on any breach of the Rules they see or are told about. This applies whether the referee is assigned to one group for the entire round or to monitor multiple groups, certain holes or parts of the course.

A referee's duties may be limited by the Committee in match play and stroke play.