Ethiopian Gebrselassie, a multiple Olympic and world champion over 10,000 metres as well as a former marathon world record holder, will pace the first 30 km at world-record speed at the April 13 event, five days short of his 41st birthday.
A strong field will include Britain's double Olympic and world champion distance runner Mo Farah, marathon world record holder Wilson Kipsang and fellow Kenyan and London course record holder Emmanuel Mutai.
Olympic marathon champion Stephen Kiprotich of Uganda and London champion Tsegaye Kebede of Ethiopia will also compete.
"Haile is an icon of distance running, a man who has broken 27 world records on the track and road during his long and brilliant career, and we can't think of anyone better to set our elite men up for a crack at the world marathon record," race organiser Hugh Brasher said in a statement.
"Everyone knows how difficult it is to break the world record on London's course, especially with such a competitive field, but with Haile pacing and four of the fastest marathon runners in history in the race, there's a real chance we will see something special."
Gebrselassie ran the London marathon three times, coming third in 2002.