Mary Jepkosgei Keitany is a Kenyan former professional long distance runner. She was the world record holder in a women-only marathon, having won the 2017 London Marathon in a time of 2:17:01. As of November 2022, she placed fifth on the world all-time list at the marathon and eleventh on the respective world all-time list for the half marathon.

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.