Simon Chemoiywo (born 20 April 1968) is a Kenyan former long-distance runner.
He competed in track, cross country and road running.
At the IAAF World Cross Country Championships he twice represented Kenya: in 1994 he was the runner-up and team champion, then helped retain the team title for Kenya at the 1995 race.
He was the African champion in the 5000 metres in 1993 in a championship record and was a silver medallist at the same event three years later.
He was a one-time Kenyan champion in the 5000 m, in 1994, and competed for Kenya in that event at the 1995 World Championships in Athletics.
He holds personal bests of 13:07.57 minutes for the 5000 m and 27:25.82 minutes for the 10,000 metres.
In road events he was twice winner of both the Saint Silvester Road Race and Vancouver Sun Run.
He made his marathon debut in 1998 and set his best of 2:10:35 hrs while winning the Prague Marathon.