[2] At the 2017 Italian National Championships in April 2017, Martinenghi set a new world junior record in the long course 50 metre breaststroke with a time of 26.97 seconds.

[7] On 22 May, two days later, he won a bronze medal in the 50 metre breaststroke, finishing in a time of 26.68 seconds to round out the podium with gold medalist Adam Peaty of Great Britain and Ilya Shymanovich of Belarus.

[10] At the Olympic Games, held in July and August 2021 in Tokyo, Japan, he swam a 58.28 in the semifinals of the 100 metre breaststroke to set a new Italian record in the event and qualify for the final.

[15] For his first final at the 2021 European Short Course Swimming Championships, held in November at the Palace of Water Sports in Kazan, Russia, Martinenghi helped set a new world record of 1:30.14 and win the gold medal in the 4×50 metre medley relay, splitting a 25.14 for his 50 metre breaststroke portion of the relay.

[17][18][19] In the semifinals of the 50 metre breaststroke two days later, he set new Championships and Italian records with a time of 25.37 seconds to qualify for the final ranking first.

[24] In December, at the 2021 World Short Course Championships in Abu Dhabi, United Arab Emirates, Martinenghi won the silver medal in his first event, the 100 metre breaststroke, with a time of 55.80 seconds, which was 0.10 seconds slower than the gold medalist and world record holder in the event Ilya Shymanovich.

[25] Helping achieve a third-place finish with a 1:37.29 in the final of the 4×50 metre mixed medley relay for his second event, he won a bronze medal for his efforts.

[26] For his third event, he split a 25.30 for the breaststroke leg of the 4×50 metre medley relay, helping win the bronze medal with a final time of 1:30.78.

[28] Concluding competition with his fifth event, he split a 55.94 for the breaststroke leg of the 4×100 metre medley relay to help achieve a new Championships and Italian record time of 3:19.76 with finals relay teammates Lorenzo Mora (backstroke), Matteo Rivolta (butterfly), and Alessandro Miressi (freestyle) and win the gold medal.

[33][34][35] In the preliminary heats of the 100 metre breaststroke at the 2022 World Aquatics Championships on 18 June, Martinenghi qualified for the semifinals ranking fourth with a time of 59.06 seconds.

[49][50] The first day of the 2022 European Aquatics Championships, held in Rome in August, Martinenghi ranked first in the preliminaries of the 100 metre breaststroke, qualifying for the evening semifinals with a time of 59.08 seconds.

[54][55][56][57] Later in the same session, he helped win a silver medal in the 4×100 metre mixed medley relay, splitting a 58.13 for the breaststroke leg in the final.

[76] Finishing in a time of 56.60 seconds for the preliminaries of the 100 metre breaststroke on day two of the 2022 World Short Course Championships in Melbourne, Australia, Martinenghi advanced to the semifinals ranking first.

[77] In the evening, he helped achieved a European record time of 1:36.01 in the 4×50 metre mixed medley relay final to win the silver medal, splitting a 24.83 for the breaststroke portion.

[90] For the final of the 50 metre breaststroke on the sixth and final evening of competition, he achieved a silver-bronze finish with fellow Italian Simone Cerasuolo, finishing 0.26 seconds ahead of Cerasuolo in a time of 25.42 seconds to help accomplish the maneuver and mark the first time it was achieved at a World Short Course Championships by any two men from one country.