Former world marathon record holders Wilson Kipsang and Tegla Loroupe, as well dozens of other walkers, crossed the finish line in Kenya's Rift Valley, where over 300 people have been killed in clashes this year.
Rivalries between pastoralist communities competing for scarce resources, such as livestock and water, are worsened by easy access to automatic weapons and the absence of state security officers.
"We have braved the sun and the rains, and even sometimes put our lives at danger," said organiser John Kelai, a former Commonwealth marathon champion, who decided to stage the event after seeing three of his uncles killed in cattle raids.
The 22-day trek, which saw communities along the route join the walk, took place through some of the hardest-hit areas.
"Without peace we cannot nurture the young talent," said Kipsang. "This area is affected so much with cattle rustling it is impacting development."
Ethiopian running legend Haile Gebrselassie has backed the walk. Organisers had hoped he would attend the finale, but in the end he was unable to make Thursday's celebrations.
"When people are being killed and driven from their homes, it is a tragedy for all of us," Gebrselassie said in an earlier statement.
The marathon march began in Kenya's northern town of Lodwar in the volatile Turkana region on July 15, heading south for some 40 kilometres (25 miles) every day.
- Over 300 killed -
The UN on Wednesday said at least 310 Kenyans have been killed and over 215,000 forced from their homes this year in ethnic violence in northern Kenya.
While violence between rival groups is common in Kenya's northern Rift Valley regions, the number killed and forced to flee in the first six months of this year is already the same as the total for all of 2014.
In May, some 75 people were killed in just four days of cattle raids and revenge attacks.
In 2014, 310 people were killed, 214 wounded and 220,000 displaced, according to the UN.
Dancing and singing, the community around Lake Bogoria celebrated as the walkers crossed the final line.
"It is so good to see all these communities here together," said Loroupe, the first African woman to win the New York City Marathon, who will also take part.
The athletes, who were accompanied by communities affected by the violence in their walk, have raised over $90,000 (82,000 euros) towards funding a peace-building programme, said the Aegis Trust, which works to rebuild communities riven by conflict, notably in Rwanda after the 1994 genocide.
Aegis Trust, which helped organise the walk, said the programme will engage thousands of "young people at risk of being drawn into the ethnic violence, saving lives."
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