The man popularly thought to have the biggest arms in the world is Gregg Valentino, an amateur bodybuilder, who at his biggest, reportedly had 28” arms.
But, this ‘title’ is controversial, and dubious, at bes
It is widely accepted that Gregg Valentino has used an oil-like substance (some say synthol, although Gregg denies it he admits using another similar substance) which is injected into the muscles to expand their volume, giving the appearance of bigger muscles, though the actual development of the fibres simply isn’t there. By many peoples views, this makes his claim to worlds biggest arms illegitimate.
Although, it’s worth noting that for all his faults and obvious synthol (or similar) usage, Gregg Valentino was actually a very big bodybuilder with huge arms when he was a regular, proportioned bodybuilder before he decided to take the path towards freakdom. But… he certainly wouldn’t have been close to having the biggest arms in the world in his regular state, and it goes without saying that even most run-of-the-mill IFBB pro bodybuilders would have had bigger arms.
Then there are other people, who don’t even have the basic muscle development of Gregg who have injected God knows what into their arms and look absolutely ridiculous. I have seen photographs of guys who possibly had bigger arms than Gregg Valentino did, but some look as if they never even lifted weights before in their lives, and just pumped gallons of oil into their arms.
If we’re talking about the biggest arms which haven’t come from synthol or similar, I do believe 8X Mr. Olympia Ronnie Coleman has/had the biggest non-synthol arms in the world, reportedly somewhere between 21.65” as measured on a TV show, to 24” when in training at his biggest.