A statement on Friday said leading athletes will run with amateurs in a mass participation event across closed roads in London on March 4.
A total of 7,500 places will be reserved for community groups from the four host boroughs in the race.
"We are creating an event that is unique, that is fun, that people will want to come back to year after year," said event director Hugh Brasher. "The Big Half is a celebration of community and life."
As part of the campaign, plans have also been announced for a run for younger competitors, a relay for community groups and a festival in Greenwich.
The London Marathon was co-founded by Brasher's father Chris, in 1981. Around 40,000 runners took part in last Sunday's race, with an estimated 800,000 supporters lining the route.
(Reporting by Neil Robinson, editing by Mitch Phillips)
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