Deriba Merga Ejigu is an Ethiopian professional long-distance runner. He mainly competes in the marathon. He finished fourth in that event at the 2008 Beijing Olympics and went on to win the Boston Marathon the following year. His personal best for the distance is 2:06:38 hours.

A half marathon is a road running event of 21.0975 kilometres —half the distance of a marathon. It is common for a half marathon event to be held concurrently with a marathon or a 5K race, using almost the same course with a late start, an early finish or shortcuts. If finisher medals are awarded, the medal or ribbon may differ from those for the full marathon. The half marathon is also known as a 21K, 21.1K, or 13.1 miles, although these values are rounded and not formally correct.