Gert Jan Timmerman (born 15 April 1956) is a Dutch chess player, most famous for being the fifteenth ICCF World Champion in correspondence chess, 1996–2002.
Before becoming the fifteenth World Correspondence Champion, TImmerman won Final B of the 5th World Cup between 1987 and 1994.He tied for second place behind Mikhail Umansky in a "champion of champions" tournament, the ICCF 50 Years World Champion Jubilee.
This was a special invitational correspondence tournament involving all living former ICCF World Champions.