Raymond Greenfield, 33, was drinking in the Original Oak in Headingley with friends ahead of the match against Toulouse Olympique on Saturday when he was taken ill.
He is believed to have suffered a cardiac arrest and died in Leeds General Infirmary after other drinkers had desperately tried to administer CPR.
Raymond, from Burley, was well-known among Rhinos supporters and was nicknamed No 1 Ambassador in recognition of his love for the club.
His father Douglas posted a tribute to his son on Facebook:-
"My eldest son Raymond passed away today after collapsing among friends whilst having a pre-match drink before the Rhinos match at Original Oak."He was helped straight away by two guys until paramedics arrived within two minutes."They tried for 40 minutes but could not re-start his heart and he died in the LGI ."Many thanks to all that helped, even to the guy who ran down the road for the defibrillator."Wonderful 33 years of loving memories. Thanks also to the Rhinos friends I met later on."
A Justgiving page has been set up to raise money for a Rhinos-themed floral tribute to display at Raymond's funeral, and it has already exceeded the Â£600 target.
Daniel Frank, who set up the appeal, said:
"Ray was a regular contributor to many rugby league forums and had many friends at Leeds Rhinos. We hope to raise enough money to buy a floral tribute for his funeral (of course, it will be blue and amber!); if you are able to support us, please do. Any extra funds will be donated to Ray's family or a charity of their choice."
Leeds Rhinos’ head of customer experience, Sian Jones, said:
“We were deeply saddened to hear the news about Raymond.
“He was a fantastic supporter of the club and one of our first ambassadors, who did a tremendous job of supporting the club out in the community.
“Our thoughts and prayers are with his family and friends at this time.”
Donate to the appeal here.