Depending on the level of competition but I shall assume the highest level, there are 5.
In international/super 14 Rugby for example there is the referee that blows the game on the field. He is supported on either touch line by one Touch Judge (TJ). There are therefore 2 TJs. They help the referee with line out positions, off side calls, foul play calls, conversion/penalty kicks/drop goals, and other general matters is assistance to the referee and on their recommendation to the referee penalize the offenders accordingly.
TJ1 is the first reserve in case of an injury to the referee and TJ2 is the second reserve. TJ3 would be a reserve to TJ2 (but not running touch) rather tending to any side line activities such as "blood replacements" and substitutions.
Lastly there is the Telly Match Official (TMO). The referee will call a "time out" and request that the TMO give judgment over the awarding, or not, of a try.
In a rugby match there is the 1 main referee and 2 touch judges.
Today, in Rugby League there are two main referees on the field, two touch judges and one video ref
Chat with our AI personalities
In regional rugby union there is a 1 -referee - 2 assistant referees - a TMO(television match official) on occasion and a citing official
In standard games you have - 1 referee and 2 assistant referees