Seven-year-old JR has horns that measure an incredible 9ft 1ins - and they are likely to grow even bigger.
But even though he has a name derived from a character in Dallas, the ultimate Texas television show, JR does not reside in the U.S.
Instead, he is part of the largest herd of Texas Longhorns in Australia, roaming around the 1,100acre Leahton Park estate in Queensland.
He has claimed the Guinness World Record from a bull in Ohio called Shadow Jubilee.
But whereas that animal had horns that are 88ins long, JR's measure a staggering 109ins from tip-to-tip.
JR is descended from pure Texas Longhorn stock.
His owner Michael Bethel, 50, who runs Leahton Park with his wife Lynda, 39, began breeding Longhorns 14 years ago.He said: 'I don't think JR realises how much attention he's getting now he's a record breaker.
'He's just happy and healthy, we don't give him any special treatment, we just let him graze around with the kangaroos like the rest of the heard.
'He's only seven so he still has a bit of growing to do yet - they can live until their early 20s - his horns could still get bigger.'
The park opened as a tourist attraction three years ago to allow visitors to take horse-drawn wagon tours to see the Longhorns.