The McLaren driver will end a career that began with a debut for Minardi at the Australian Grand Prix of 2001.

Alonso, 37, who is competing in his 17th F1 season, won the 2005 and 2006 championships when racing for Renault.

"After 17 wonderful years in this amazing sport it's time for me to make a change and move on," he said.

"I made this decision some months ago and it was a firm one. There are still several grands prix to go this season, and I will take part in them with more commitment and passion than ever," he added.

"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."

Alonso has in recent years branched out into other series and in June he won the Le Mans 24 Hours sportscar race at his first attempt.

He joined Toyota's World Endurance Championship (WEC) programme this season with the aim of winning Le Mans, and has dovetailed it with F1.

That victory provided him with the second part of motorsport's 'triple crown'. Twice a Monaco Grand Prix winner, he is only missing Indianapolis 500 success.

He competed in the Indy 500 for the only time to date in May 2017, retiring towards the end of the race with engine failure, having run strongly throughout and led for a total of 27 laps.

Only Englishman Graham Hill has won all three classic races in the history of motorsport.