Running a marathon (42K) in two hours is a definitely an incredible human feat. It requires a pace of no less than 4 minutes and 34 seconds per kilometer throughout the whole 42-kilometer distance. I made a little research and discovered that Patrick Makau of Kenya currently holds the world record for a marathon with an official time of 2:03:02 during the Berlin Marathon last September 25, 2011. This world record is officially recognized by the International Association of Athletics Federations.
So no human being has ever achieved a 2-hour marathon yet. But to give us an idea on what a 2-hour 42K run will look like, here's a short video of an athlete demonstrating (on a treadmill) the speed necessary to complete a marathon in four, three and two hours:
What about you? Do you have a time goal in your next marathon? I've yet to run my first 42k and since I'm a slow runner (my half-marathon best is only 2:13), I would be satisfied if I finished it in 5 to 6 hours. A sub-5 run for me would already be a miracle! : )