The NRL celebrated the 100th birthday of former referee Robert Culkin.

The NRL has been saddened today by the passing of Robert Culkin this morning.

Culkin, who was the oldest grade referee, the oldest member of the New South Wales Referees Association as well as the oldest member of the Men of League Foundation, turned 100 in July this year.

NRL CEO Todd Greenberg said Mr Culkin was a remarkable and endearing figure who would be missed.

"Only a few months back, we celebrated Robert's 100th birthday during an event in the Heroes and Legends Museum," Mr Greenberg said.

"Every time you spoke to Robert you could tell how passionate he was about officiating and about Rugby League.

"He took his refereeing tickets with him to official functions and spoke with so much pride about his achievements."

At his 100th birthday celebrations, Mr Culkin had the honour of presenting the State of Origin III referees with their jerseys.

NRL General Manager Officiating Tony Archer said officials would wear black armbands for the remainder of Round 26 to acknowledge Mr Culkin's passing.

"Our referees always enjoyed spending time with Robert and he was someone all of our officials looked up to," Mr Archer said.