The win was Ferrari's 250th in Formula 1 and came at the Silverstone circuit where the championship started in 1950 and in front of a capacity race-day crowd of 175,000.
On a day of changing fortunes, with Red Bull's Max Verstappen crashing out four laps from the finish to trigger the safety car, George Russell got lucky and finished second for Mercedes to close the points gap to his 19-year-old Italian teammate.
Seven-time world champion Lewis Hamilton completed the podium in third place for Ferrari, overcoming a five-second penalty for jumping the start, but the Briton finished the race under investigation for a potential yellow-flag breach.
There was additional confusion over the safety car, with a message suggesting it would pit to allow one last lap of racing only for it to then stay out until the last corner and rob the crowd of a potentially thrilling final dash to the line.
Hamilton had pitted for fresh tyres, dropping from second to third, while Russell - behind his compatriot on track - stayed out in a gamble that ultimately paid off when it emerged that there was no chance of him being overtaken.
Antonelli, who started on pole position and looked likely to win, had been closing on leader Leclerc with 11 laps to go when he slowed and alerted the team to a problem with the car. The 19-year-old Italian finished 16th.
"It feels incredible. Unfortunately the end was maybe not the one I would have dreamt of," said Leclerc of his first win since 2024.
"With Kimi, it would have been close. He was very fast when he was coming towards me. It would have been very difficult to keep that first place. Then I heard he had a problem so I was like 'Okay, now I have a big gap and it should be straightforward'.
"(It was) not great for the fans around the track but in the helmet I was happy that there was not a restart to keep that win."