For his first meet of 2016, Wellbrock returned to Luxembourg for the 18th Luxembourg Euro Meet, where he competed in serveral events, including placing seventh in the 1500 metre freestyle with a time of 15:27.19.[6][2]
Wellbrock continued to improve at his main distance freestyle events, placing first in the 1500 metre freestyle at the Norddeutsche distance champs with a time of 15:19.41.[7]
2016 Olympics qualification
In May 2016, Wellbrock returned to the German Swimming Championships (long course), where he competed in the 200 metres butterfly, 400 metres freestyle and 1500 metres freestyle. In the 1500 metres freestyle, Wellbrock set a new personal best of 14:55.49 which beat his previous long course record of 15:08.05, broke the 15 minute barrier, broke the under-20 age group record and put him in the top 10 1500 metre freestyle swimmers for that year.[8][2] Additionally, since the time was under the 15:02.37 Olympic nomination standard, Wellbrock qualified for 2016 Summer Olympics.[9] With this time, Wellbrock was just over 5 seconds off the German national record of 14:50.36 set by Jorg Hoffman in 1991, which was a world record at the time.[8]
2016 Olympics preparation
In preparation for the Olympics Wellbrock entered one last international meet, the Meeting International de Canet-en-Roussillon 2016 (long course), where he placed twenty-seventh in the 400 metres freestyle and first again in the 1500 metres freestyle with a time of 15:00.71, just over 5 seconds outside of his personal best.[2]
2016 Rio Olympics
At the 2016 Summer Olympics, Wellbrock swam in the heats of the 1500 metres freestyle, where he finished with a time of 15:23.88 which was just under 30 seconds slower than his personal best set around 3 months earlier.[2][10][11][12] This time did not qualify him for the final.
2016-20
Only 19 days after his Olympic debut, Wellbrock returned to competition at day two of the 2016 FINA World Cup in Berlin, where he again finished first in the 1500 metre freestyle with a time of 14:35.79.[13][14]
A few months later, Wellbrock competed at the 2016 North Sea Meet, where he finished first in all three events he competed in: the 400 metres freestyle, 1500 metres freestyle and 200 metres butterfly. In both the 400 metres freestyle and 200 metres butterfly, Wellbrock set new personal bests of 3:49.02 and 1:59.68 respectively.[15][2]
To finish off 2016, Wellbrock competed in the FINA World Swimming Championships (25 m), where he placed thirty-second in the 400 metres freestyle with a time of 3:47.30 and seventeenth in the 1500 metres freestyle with a time of 14:52.00.[2]
To start 2017, Wellbrock competed at Swim Open Stockholm, where he placed third in the 1500 metres freestyle with a time of 15:02.91 and second in the 400 metres freestyle with a time of 3:48.38.
Wellbrock qualified to represent Germany at the 2020 Summer Olympics, held in Tokyo, Japan and postponed to summer of 2021 due to the COVID-19 pandemic.[19] His first medal of the Olympic Games was in the 1500 metre freestyle, where he won the bronze medal.[20] Wellbrock also won a gold medal in the 10 kilometre open water swim a few days later with a time of 1:48:33.7, which was over 25 seconds faster than the second-place finisher.[21] His gold medal was the first won in the event at an Olympic Games by a swimmer representing Germany.[20] His Olympic medals in pool swimming and open water swimming marked the second time a swimmer won medals in both disciplines at one Olympic Games and he was closely followed by the third swimmer to do so, Gregorio Paltrinieri of Italy who also won a medal in each discipline at the 2020 Summer Olympics only Gregorio Paltrinieri won his second medal, a bronze medal in the 10 kilometre open water swim, seconds after Welllbrock and thus Wellbrock became the second swimmer in history to achieve the feat and Gregorio Paltrinieri the third.[22]
2021 European Short Course Championships
At the 2021 European Short Course Swimming Championships, held at the Palace of Water Sports in Kazan, Russia, Wellbrock won a gold medal in the 1500 metre freestyle on 4 November with a time of 14:09.88.[23] On 7 November, Wellbrock won the silver medal in the 800 metre freestyle in 7:27.99, finishing five-hundredths of a second behind gold medalist in the event Gregorio Paltrinieri.[24]
2021 World Short Course Championships
At the Abu Dhabi Aquatics Festival, held in parallel with the 2021 World Short Course Championships, in December 2021, Wellbrock won a bronze medal as part of the open water 4×1500 metre mixed relay event.[25] In his individual event, the 10 kilometre open water swim, Wellbrock won the gold medal in a time of 1:48:09.4, finishing over two seconds ahead of silver medalist Domenico Acerenza of Italy.[26] As part of the World Championships, Wellbrock swam a 14:25.79 in the prelims heats of the 1500 metre freestyle on 20 December, qualifying for the final the following day ranking third.[27] In the final of the 1500 metre freestyle, Wellbrock set a new world record with a time of 14:06.88 and won the gold medal.[28][29][30] Wellbrock also co-hosted a swimming clinic at the venue of the World Championships, Etihad Arena, with Anthony Ervin of the United States.[31]