As a child, Fannemel mainly devoted himself to biathlon . Since 2004, however, he has concentrated on ski jumping training at his home club in Hornindal . Fannemel played his first ski jumping competition in the FIS Cup on September 8, 2007 in Falun . This was followed by further jumping in the FIS Cup and the Continental Cup . He was able to achieve his first victory on October 12, 2008 in the FIS Cup. On the hill in Einsiedeln , Switzerland , he won ahead of Klemens Murańka and Pascal Bodmer . His first win in the Continental Cup was on August 23, 2009 at Lysgårdsbakken in Lillehammer ahead of Erik Simon . On December 4th and 5th, 2009, he completed his first two World Cup appearances on the same hill . Fannemel finished the first competition in 37th place. In the competition that followed, he managed the second longest jump in the second round with 135.5 meters. With the 10th place he gained his first World Cup points.
At the Junior World Championships 2011 in Otepää , Estonia , he finished fourth in the individual and third with the team. At the Norwegian Championships on the large hill in Trondheim in February 2012 , he made it onto the podium for the first time with third place. On February 11, 2012, he and the Norwegian team won the opening competition of the FIS Team Tour on the Mühlenkopfschanze in Willingen and thus achieved his first World Cup victory. At the Norwegian Summer Championships 2012 in Oslo, he was able to win his first national title. On November 25, 2012 in Lillehammer - where he had already scored his first World Cup points three years earlier - he achieved his first podium finish in a World Cup with second place.
In February 2014, Fannemel took part in the Winter Olympics for the first time in Sochi . He was 15th in the individual on the normal hill and fifth in the individual on the large hill. With the Norwegian team he finished sixth. In the 2014/15 season took Fannemel his first two individual World Cup victories. He scored his first victory on December 13, 2014 in Nizhny Tagil and the second on February 8, 2015 in Titisee-Neustadt . On February 15, 2015 he improved Peter Prevc's ski flying world record by 1.5 meters and was the ski flying world record holder with 251.5 meters until March 18, 2017, when Stefan Kraft replaced him. At the Nordic World Ski Championships in Falun in 2015 , he finished ninth in the individual competitions on the normal hill and seventh on the large hill. In the team competition he won the world championship title together with Anders Bardal , Anders Jacobsen and Rune Velta in front of the teams from Austria and Poland. In the 2014/15 season he achieved a total of seven individual podium finishes in the World Cup and 1161 points, finishing fourth in the top ten in the overall World Cup for the first time.
At the 2016 Ski Flying World Championships on the Kulm , he finished seventh in the individual competition and in the team competition he won the gold medal together with Johann André Forfang , Daniel-André Tande and Kenneth Gangnes . On January 31, 2016, he achieved his third individual World Cup victory in Sapporo . In summer 2016 he jumped very successfully in the Grand Prix . On July 22nd, he won his first Grand Prix competition with the Norwegian team. The first victory in an individual competition followed in Hakuba on August 27th . Overall, he jumped three times on the podium in individual competitions and ended up in seventh place in the overall standings with 260 points. This was his best result up to that point. At the Nordic World Ski Championships in Lahti in 2017 , he finished fifth in the individual competition on the large hill after not being used on the normal hill. In the team competition he won the silver medal behind Poland together with Johann André Forfang, Daniel-André Tande, and Andreas Stjernen .
On December 16, 2017, he achieved his fourth individual World Cup victory in jumping in Engelberg . With jumps of 133.0 meters in the first round, which gave him an eight point lead over Kobayashi, who was second at the time, and 127.5 meters in the second round, he finally defeated the second-placed German Richard Freitag with 253.6 to 253, 5 points by about 5 centimeters and thus the smallest possible lead. At the Four Hills Tournament 2017/18 he was able to convince with two podium places as third in Garmisch-Partenkirchen and second in Bischofshofen . He was also seventh in Oberstdorf and 16th in Innsbruck . As a result, he landed on the podium in the overall tour stand for the first time. He was third behind Kamil Stoch and Andreas Wellinger. At the 2018 Winter Olympics in Pyeongchang , he was part of the five-man Norwegian squad. However, it was not used in any of the three competitions.
On July 18, 2019, Fannemel was seriously injured during a training jump in Wisła when he could not stand his jump at 140 meters from the Adam-Małysz-Schanze , which has its hill size at 134 meters. A cruciate ligament and meniscus injury was diagnosed in Norway, preventing him from participating in the 2019/20 season.
Private
Fannemel has three siblings. His twin brother Einar and his older sister Eline are both biathletes, Rasmus, who is two years older, is not active in sports. Fannemel also has two cousins who are also ski jumpers, Lorentz and Brede.