Kebede won the race in 2010, posting an impressive time of 2 hours, 6 minutes, 4 seconds, more that 29 seconds ahead of second-place finisher Emmanuel Mutai of Kenya. Since 2004, Kebede is the sole non-Kenyan to win the race.
Last year's race will be best remembered by many of the runners wearing black ribbons to honor the bombing victims of the Boston Marathon, held one week earlier. A moment of silence was held before the start of the race, and security was extremely tight for the spectators and the 36,000 runners.
Making his marathon debut will be Mo Farah of Great Britain. He won the gold medal in the men's 5,000 and 10,000 meters at the 2012 London Olympics.
Farah tuned up for this year's event by running the first half of last year's marathon.
"I gained a lot of valuable experience running part of the course alongside the top guys last year and can't wait to race the full distance in April," the 30-year-old told the London Marathon website.
Among the other runners in the field are Mutai, the course record holder; Kipsang, who set the world record in the Berlin Marathon at 2:03.23 last September; world marathon champion and Olympic champion Stephen Kiprotich of Uganda; and two-time New York City champion Marilson dos Santos of Brazil.
The top American last year was Patrick Rizzo from Illinois. He finished a respectable 12th at 2:16.05.
This year's race also will feature a pacemaker - Ethiopia's Haile Gebrselassie, who will turn 41 five days after the London Marathon. He is expected to lead the pack to the 30-kilometer mark, before bowing out.
Gebreselassie won two Olympic and four World Championship gold medals at 10,000 meters. Back in 2008, he won the Berlin Marathon in a world-record time of 2:03.59, breaking the old mark by 27 seconds.
Kipsang set the world record last September at the Berlin Marathon. With a world record pacemaker leading the way, runners will have to average better than 4 minutes, 43 seconds every mile to break Kipsang's mark.
Another emerging star from Gebrselassie's nation of Ethiopia is Tsegaye Mekonne. The 18-year-old ran his first marathon earlier this year in Dubai and beat an experienced field in 2:04.32
The women's division will be headed by defending champion Priscah Jeptoo of Kenya. Jeptoo, who posted the second-fastest marathon time of 2:20.14, has five career marathon victories since 2009 and won the Olympic silver medal in 2012. She also won the New York City Marathon in 2013.
Ethiopia's Tiki Gelana, the 2012 Olympic gold medalist, world champion Edna Kiplagat of Kenya and two-time Olympic 10,000 champion Tirunesh Dibaba of Ethiopia are among the top contenders. All three have run under 2:20.00.
The world record stands at 2:15.24, set by Britain's Paul Radcliffe in London in 2003.