Matti Mattsson (born 5 October 1993 in Pori) is a Finnish swimmer and Olympic medalist. At the club level, Mattsson represents the Pori Swimming Club. He is coached by Eetu Karvonen. Mattsson has achieved the Olympic bronze in 2021 and the World Championship bronze in 2013 in the 200-meter breaststroke.
Mattsson first reached the Adult Level Championship medals at the age of 15 in the summer of 2009, when he won bronze in the 100m breaststroke. At the Youth Olympic Festival in Tampere the same summer, he won a silver medal on the same trip. In 2010, Mattsson finished eighth in the 200m breaststroke at the Youth Summer Olympics in Singapore. In January 2011, Mattsson won the Finnish short track championship in the 200-meter breaststroke with more than five seconds ahead of the silver medalist. Later in the spring, Mattsson broke the OST limit for the 2012 London Summer Olympics, on the basis of which he was later awarded an Olympic seat based on FINA points. In the summer, Mattsson won the Finnish Championship silver in the 100-meter breaststroke. At the beginning of July, she swam the Finnish record of 2.13.28 in the 200-meter breaststroke in the junior European Championship semi-finals. The previous record set by Jarno Pihlava in 2002 improved by about half a second. In the final, he improved his SE by more than 0.6 seconds to 2.12.65 and won the European Championship silver in the youth. Mattsson's time on November 2, 2001 was a new Finnish record, and he was 15 seconds behind the semi-finals. The Finnish Swimming Association chose Mattsson as the best Finnish swimmer of 2012. In January 2013, Mattsson swam the 200-meter breaststroke SE 2.07.50 in the short track Finnish Championships. The previous SE had been in the name of Jarno Pihlava since 2002. At the 2013 World Championships in Barcelona, Mattsson won bronze in the 200-meter breaststroke with a new Finnish record of 2.08.95. He had improved Finland's record already in the first round at 2.10.16 and in the semi-finals to 2.09.96. Mattsson's bronze medal was Finland's first World Long Distance Swimming Medal since 2003. Mattsson did not participate in the 2013 Short Track European Championships after falling on a bicycle in August and having to have surgery in November. In January 2014, Mattsson was chosen Pori Athlete of the Year 2013. He was also awarded the Finnish Sports Gala's Breakthrough of the Year 2013.In early 2016, Mattsson changed his diet and lost 12 kilos as a result. In the London Long Track European Championships in May, he placed fifth in the 200m breaststroke. At the 2016 Rio de Janeiro Olympics, Mattsson swam to 11th place in the preliminary rounds of the 200-meter breaststroke with a time of 2.10.09 but finished last in the semi-finals and was eliminated. After the Olympics, Mattsson's coach changed when Eetu Karvonen replaced Tomi Pystysen, who coached him in 2008–2016.
In the 2017 Finnish Championships, Mattsson swam the Finnish record in the 100m breaststroke record at 1.01.12. Jarno Pihlava's former record in 2000 improved by five hundredths. In the opening rounds of the 2018 World Championships in swimming, he improved to a record time of 1.00.86. In March 2021, he improved the Finnish record to 1.00.57. In the long track European Championships 2021, Mattsson improved the Finnish records in the 100-meter and 200-meter breaststroke both in the first round and in the semi-finals. In the 100 meters, he swam in the semi-finals for 59.99, finishing 13th. In the 200 meters, he swam in the semi-finals for 2.08.26 and in the final for 2.08.48, finishing fourth. In the final, he improved his record time in Finland by more than a second to 2.07.13 and reached the Olympic bronze. In January 2022, Mattsson was named Athlete of the Year 2021.