William Cheruiyot Sigei (born 11 October 1969 in Cheboi'ngong' village, just outside Kapsimotwo village, Bomet, Kenya) is a former Kenyan long-distance runner who won the IAAF World Cross Country Championships in 1993 and 1994. In 1994 he set a new world record over 10,000 metres in Oslo with 26:52.23 minutes.

As of 2021, he is ranked thirty seventh of all times over 10,000 metres. The current world record is 26:11.00 minutes, and belongs to Joshua Cheptegei of Uganda.^[1]

• William Sigei at World Athletics
• Okoth, Omulo (17 March 2007). "A Kenyan XC legend - William Sigei". IAAF. Retrieved 2007-03-19.