The two-time world champion announced the decision mid-way through Formula 1’s summer break, amid what has been another disappointing season with the McLaren team.

"After 17 wonderful years in this amazing sport,” Alonso said, “it's time for me to make a change and move on. I have enjoyed every single minute of those incredible seasons and I cannot thank enough the people who have contributed to make them all so special.

"There are still several grands prix to go this season, and I will take part in them with more commitment and passion than ever.

"Let's see what the future brings; new exciting challenges are around the corner. I'm having one of the happiest times ever in my life but I need to go on exploring new adventures."

This season’s switch by McLaren from uncompetitive Honda to the Renault powerplant had been aimed at restoring the team’s fortunes and placating an increasingly frustrated Alonso. However, an uncompetitive 2018 chassis pack from McLaren has seen the team arguably take a step backwards from the previous season.

The decision to quit F1 frees Alonso to chase his dream of success at Indianapolis. McLaren had allowed Alonso to miss the Monaco Grand Prix last year so that he could race in the Indy 500, while this year the team did not object to him competing with Toyota in the World Endurance Championship – which saw the Spaniard win the Le Mans 24 Hours.

McLaren boss Zak Brown paid tribute to Alonso: "Fernando is not only an outstanding ambassador for McLaren but also for Formula 1.

"His 17 years in the sport, as arguably the pre-eminent driver of his generation and undoubtedly an F1 great, have added another layer to Formula 1's rich history.

"There is a time for everyone to make a change and Fernando has decided the end of this season to be his.

"We respect his decision, even if we believe he is in the finest form of his career."