Quite simply, the Greatest Bicycle Racer of All Time.
Nicknamed "the Cannibal", Eddy Merckx owned the European Road Bicycle Racing scene during his 14 year career spanning 1965-1978. At his peak, he won over 35% of the races he entered. Which is amazing, when you realize each race has ~100 racers (unlike Football or Baseball, where there's only 2 teams trying to win). In countries where bicycle racing is a recognized sport, Eddy Merckx is widely recognized as the best athlete of his time.
A five-time winner of the Tour de France (just one of four ever to do so), the Giro d'Italia, and countless other major bicycle races. Until recently, holder of the one hour record on a 'standard' bike. (Which means, the longest distance covered in one hour. The record was recently beaten by British bicycle racer Chris Boardman.)
His nickname was given to him because of the manner in which he won his races. In stage races such as the Tour de France, the overall leader frequently just rides in order to protect his overall lead by just riding fast enough to stay ahead of people that have total elapsed time near his own. Merckx, on the other hand, made what seemed like suicidal moves in order to win that day's stage, even while in the overall lead. Also, in professional road racing, there's some element of trading victories in minor races for a promise of cooperation in later races. Merckx would have none of that, and treated every race he entered as if he would die if he didn't win them.
Because he was so successful, people either loved him or hated him. In one of the races in which he didn't win, a spectator kidney-punched him. Other racers of the time were known to celebrate not victory, but Eddy Merckx not winning.
Due to the modern idea of periodization for peak athletic performance, and specialization of bicycle racers, it is agreed by most that no one will ever attain the level of dominance displayed by Eddy Merckx. (This is because athletes now train in order to 'peak' for certain important races, which precludes being a winner all season long as Eddy Merckx was.)
Also the name of a bicycle frame manufacturer, with which the person is associated with. During much of his career, he rode bikes that had his name on them. In fact, the bikes had a picture of Merckx on the head tube...
He is Belgian.
His son, Axel Merckx, is also a bicycle racer.
Eddy himself is now involved in commentating on bicycle races, manufacturing bikes, and is quite overweight.
The write up below brings up the prevalent doping problem in bike racing, especially in the past. Eddy has been tested positive twice during his long career, but in both cases he is adamant that he is innocent. At least in one case, it was due to a doctor prescribing a drug that had trace amounts of a banned substance, and the other time when he was disqualified from the Giro d'italia, he maintains that he was set up by the Italians. There is some evidence this assertion may be true.