On Sunday, more than 45,000 people will be taking to the streets for the annual ING New York City Marathon.
Among the runners are celebrities like Christy Turlington Burns, Ethan Zohn (Survivor: Africa), and Mario Lopez.
But this is not the first time celebrities have joined in on the grueling 26.2 mile run.
From actor Ryan Reynolds to celebrity chef Bobby Flay to magician David Blaine to Today Show personality Al Roker, the number of famous faces at the starting line has increased significantly over the years.
In 2007, Katie Holmes finished the NYC Marathon in just over five hours, and was famously greeted at the finish line by husband Tom Cruise and their 18-month old daughter, Suri.
Many criticized the actress for entering the race at the last minute and not abiding to official race entry rules. Holmes entered the race as a VIP, not through the lottery or running in one of the 26 official NYC Marathon charity runs.
Celebrities and people with name recognition are important to every sport -- it adds glitz and glamour, Richard Finn of the organizing New York Road Runners Club told Access Hollywood at the time in defending Holmes' entrance.
Cyclist Lance Armstrong, who did enter the race by running one of the 26 NYC Marathon charity events, participated in the marathon in 2006 and 2007 in support of his Lance (LiveStrong) Armstrong foundation.
Like their predecessors, most of the celebrities running the NYC Marathon this year are doing it on behalf of charities and nonprofit organizations.
Former NHL player Mark Messier, who spent 10 years playing for the New York Rangers, will be running for two organizations: Tomorrow's Children Fund and Answer the Call.
Grammy award-winning singer Mya is hoping to raise more than $200,000 for the North Shore Animal League.
Here's a look at NYC Marathon celebrity runners of the past.