The 18-year-old won by 0.16 seconds, with Australia's Jack McLoughlin taking silver and the USA's Kieran Smith bronze.
Tunisia's Ahmed Hafnaoui has shocked the swimming world with a stunning victory in the men's 400m freestyle final. The 18-year-old, who just three years ago finished eighth in the same event at the 2018 Youth Olympic Games in Buenos Aires, beat off the challenge of Australia's Jack McLoughlin and the USA's Kieran Smith to win gold.
After a lightning-fast first 200m that was under world-record pace, times slowed in the second half of the race. However, Hafnaoui grew stronger over the last 50 metres, touching the wall in 3:43.36.
Hafnaoui had entered the final as the underdog, having qualified eighth from the prelims in a time of 3:48.68. In 2019, he had stated his intent to win gold in Paris 2024, however he can now call himself an Olympic champion in Tokyo having become the fifth Tunisian to win a gold medal at an Olympic Games.
The young Tunisian swimmer has strong athletic genes, with his father Mohamed Hafnaoui a former member of the national basketball team. However, now he has written his own slice of history with a memorable victory in Tokyo.
After the race, Hafnaoui said: "I just can't believe that, it's amazing. I felt better in the water this morning than yesterday and that's it. I'm the Olympic champion now.
"I just put my head in the water and that's it. I just can't believe it. It's a dream come true."
Hafnaoui joins compatriot Oussama Mellouli, who won Olympic gold in the 10km marathon swimming event at London 2012, as the only Tunisian swimming gold medallists.
“He’s a legend. I wish to be like him someday,” Hafnaoui said of Mellouli, who also won 1500m freestyle bronze at Beijing 2008. “I was in tears. When I see the flag of my country, and I hear the anthem in the background, it was great. I’m so proud of it.”
Hafnaoui is also scheduled to compete in the 800m freestyle event that begins on 27 July, with the final taking place two days later on 29 July.