st leger
The English Grand National, not a flat race but it's run in the flat season, making it the longest race in the flat race season.
The Clonliffe 2 Mile race held its 116th edition in 2007, making it among the oldest in the world. The world's oldest marathon is the Boston Marathon which held its 112th race on April 21, 2007. The world oldest race are the Atlanteans (even though they are no longe here) they were the first known and civilised race. Hopefully that was what you meant
The Derby for flat racing or the Grand National for jumps racing (National Hunt) Ascot Gold Cup.
The oldest sporting venue in the US is Saratoga Race Course.
Sailing rocks of Death Valley Racetrack
The oldest person to run the 2016 race was Fauja Singh, who was 104 years old. Singh became the oldest person to complete a full-distance marathon, finishing the race in 3 hours, 56 minutes, and 34 seconds.
Champion Standard Open NH Flat Race was created in 1987.
Norman Vaughan
Indy 500
Sailboats and their crew are tested against each other in this classic race.
the oldest was norman Vaughan who was 88 and the youngest was dallas seavey who was 18