The points he scored were also the first of the 22-year-old Frenchman’s Formula One career in his seventh start.
“I’m still struggling to realize what’s happened today because we never expected to finish fourth in our second race weekend with Toro Rosso-Honda,” he said.
Gasly was behind only Ferrari race winner Sebastian Vettel and Mercedes pair Valtteri Bottas and Lewis Hamilton.
“I don’t actually know what to say…just unbelievable,” he declared.
Gasly, who made his debut last October at the Malaysian Grand Prix and is in his first full Formula One season, had already made an impression before Sunday’s race by setting the sixth-fastest time in qualifying on Saturday.
He started fifth after Lewis Hamilton dropped five places down the grid due to an unscheduled gearbox change.
Little did he know he would go one better on Sunday.
“We knew that the car is fast but we didn’t expect to finish in the top five,” he said. “We thought that we would be fighting with the McLaren, with the Renault, but finally the car was just so fast today and I could push flat out.”
Team boss Franz Tost hailed his heroics: “He controlled the race as if he had driven 100 races in Formula One,” he said. “It was extraordinary. It was a fantastic job today. I hope that this will only be the start.”
The result gave new power unit partners Honda a boost after a bruising three years with McLaren marked by unreliability and a lack of performance blamed chiefly on their engines.
They split with the former champions, who now use Renault engines, at the end of last season and have enjoyed a far more promising start to their partnership with Toro Rosso.
The combination looked quick and reliable in pre-season testing with none of the frustration many had predicted.
Gasly felt Sunday’s result at a power-sensitive track was validation of the progress Honda had made even if he was helped by a double retirement for Red Bull and Ferrari’s Kimi Raikkonen also failing to finish.
“They (Honda) had a tough couple of years and it’s a great way to motivate them and show them we need to keep pushing,” he said.
“To finish fourth in Formula One you need to have a good engine. So, the engine is good.”