Alonso is making the switch to pursue his ambition of winning the Monaco, Indy 500 and Le Mans
Fernando Alonso will miss the Monaco GP to race in the Indianapolis 500.
Alonso is believed to be making the switch, due to a long-held ambition of winning the so-called 'triple crown' of Monaco, the Indy 500 and Le Mans - a feat that has only been achieved once before by the late Graham Hill.
Alonso has the full approval and support of his McLaren team and engine partner Honda. McClaren have yet to decide who will be the replacement for Alonso, who has previously won the Monaco Grand Prix in 2006 and 2007.
He will be racing in a McLaren-Honda-Andretti car, and intends to start practising at Indy from 15 May onwards.
Speaking about his reasons for pursuing the Indy 500, Alonso told BBC Sport:
"It's a tough challenge, but I'm up for it. I don't know when I'm going to race at Le Mans, but one day I intend to. I'm only 35. I've got plenty of time for that.
"It's of course a regret that I won't be able to race at Monaco this year. But Monaco will be the only 2017 grand prix I'll be missing, and I'll be back in the cockpit for the Canadian Grand Prix in Montreal in early June.
"I've never raced an IndyCar car before, and neither have I ever driven on a super-speedway, but I'm confident I'll get to grips with it fast.
"I've watched a lot of IndyCar action on TV and online, and it's clear that great precision is required to race in close proximity with other cars on the far side of 220mph [354km/h]."