Olli-Pekka Karjalainen (born 7 March 1980) is a Finnish former hammer thrower. The 1998 World Junior Champion, Karjalainen is the world junior record holder with 78.33 metres (7.26 kg). His personal best throw and the Finnish record is 83.30, achieved in July 2004 in Lahti.
Karjalainen took his first medal at the 2006 European Championships by throwing 80.84. He finished second, but became the Champion in 2014 as IAAF decided to strip Ivan Tskikhan of Belarus of the gold medal for doping. Karjalainen was awarded with the gold medal in a ceremony arranged at the 2014 Finland-Sweden athletics international in Helsinki.