The ATW Welwyn Half Marathon is an autumn half marathon held in Welwyn Garden City, Hertfordshire. It begins at 9:30am from Gosling Sports Park on Stanborough Road. The start and finish are on the 400m athletics track, providing a stadium atmosphere at both ends. A 10k race is also offered on the same morning. The event is conducted under a full UK Athletics race licence, employs chip timing from Event Chip Timing, and has a three-hour time limit, after which course marshals and signage are removed.
The half marathon route departs the stadium and proceeds towards the Cole Green Way, a former railway line now functioning as a traffic-free running path. Following this section, participants undertake a brief loop, reconnect with the Cole Green Way, and then retrace their path back to Gosling Sports Park for the track finish. The 10k follows the initial 5km of the half marathon before diverging onto its own loop returning to the stadium. Warm-ups are led by personal trainers, a professional commentator announces finishers, and children can participate in a complimentary 400m fun run on the track without prior registration.