Noah Lyles Barely Beats IShowSpeed In 50-Meter Dash

Noah Lyles is the Fastest Man Alive, but the Olympic gold medalist almost lost his title to a content creator ... narrowly beating IShowSpeed in a 50-meter dash!!

The wild showdown happened on Speed's live stream on Tuesday ... and $100k was on the line. If the Team USA hero got the dub, the dough would go to charity ... and if the internet superstar pulled off the upset, a random fan would get the fat payday.

After sorting out the specifics of the race, the two crouched down and waited for MrBeast to fire the starter pistol -- and they were off!!

Speed started off HOT -- taking a quick lead for the first few strides. But, about halfway through the event, Lyles put on the jets ... and crossed the finish line in dramatic fashion.

Speed refused to believe the results ... going to iPhone footage to check out an instant replay. Even after the finish was confirmed, he explained he still felt he was faster than Lyles ... but didn't have the proper technique.

The real winner was Lyles' charity -- the Lyles Brothers Sports Foundation, which helps kids reach their dreams through athletics.

While Lyles rejected Speed's rematch request, he did offer to have the guy come train with him for a week before running it back in a 100-meter dash ... so it seems like this rivalry is far from over.