The Longest Day of Nelson is an amateur 24-hour automobile endurance race sanctioned by the Sports Car Club of America (SCCA) at Nelson Ledges Road Course in Ohio. The event takes place on or near the summer solstice each year. The host of the event was the Northeast Ohio Region of the SCCA. In 2004, 2005, and 2006, 12-hour races were held.
A 24-hour motorcycle race was also held at the circuit, ceasing in 1993.