Jari Olavi Isometsä (born 11 September 1968) is a Finnish former cross-country skier who competed from 1990 to 2006. He won three bronze medals in the 4 × 10 km relay at the Winter Olympics (1992, 1994, 1998).

Isometsä also won four medals at the FIS Nordic World Ski Championships with two silvers (4 × 10 km: 1995, 1997) and two bronzes (4 × 10 km: 1991, 10 km + 15 km combined pursuit: 1995). In the World Cup, he took four victories in races between 10 km and 30 km.

Isometsä was among the six Finnish skiers who were caught of doping in the Finnish 2001 FIS Nordic World Ski Championships scandal for taking hydroxyethyl starch (HES), a blood plasma expander usually used to cover up the use of erythropoietin (EPO) in athletes. He was stripped of his silver medal in the 10 km + 10 km combined pursuit and served a two-year suspension from the FIS, IOC, and World Anti-Doping Agency (WADA), effectively ending his career as a world-class skier.

In 2013, Isometsä received a six-month suspended sentence after the Helsinki District Court found that he had committed perjury when witnessing to the court in 2011 that he was unaware of any doping use in the 1990s.