Imagine you're a grown-up and you're running a race. You might be really good at running, but there's always room for improvement, right? Maybe you'd like to run faster than anyone ever has before! That's what the INEOS 1:59 Challenge is all about: trying to run 26.2 miles (that's like running from one end of a city to the other and then back again!) in less than two hours.
Now, that might not sound too difficult, but it's actually a really big goal. In fact, no one has ever run a marathon (that's what we call a 26.2-mile race) in less than two hours before! The current world record is 2 hours, 1 minute, and 39 seconds - which is really fast, but just a hair shy of two hours.
So, some people got together and decided to try and break that two-hour barrier. They're calling it the INEOS 1:59 Challenge. One of the best runners in the world, Eliud Kipchoge, is going to try and run the marathon in under two hours. Now, to do that, he's going to have to run really, really fast. In fact, he's going to have to run about 4 minutes and 35 seconds per mile for the entire race! That's like running a single mile in less than 5 minutes.
To help him reach his goal, they're going to make sure everything is perfect. The course will be totally flat, so he won't have to run up any hills. They'll pick a day with good weather, so that he's not battling wind or rain. And they'll even have a team of runners around him, taking turns pacing him and making sure he stays on track.
It's going to be really exciting to watch. Even if he doesn't make it under two hours, he'll still be running really, really fast. And who knows - maybe he'll break the world record too!