A Half marathon is a running race event of approximately 21.0975 km (13 miles) which is half the distance of a marathon. Usually a half marathon event is held at the same time as a marathon, using almost the same course with a late start, shortcuts or an early finish. The half marathon may also be known as 21K, 21.1K or 13.1 miles. A related event is the half ironman. Our Ironman Calendar provides a list of all half ironman events in your state. The current page lists the Half marathon road running events in your state. For your convenience we have provided a “search by state” feature for Half marathon events nearest to you. Just click on your state at the nearest events in your state will appear.