Two-time Formula 1 world champion Fernando Alonso will contest the Indianapolis 500 for a third time with the Arrow McLaren SP IndyCar outfit.
Alonso's #66 Chevrolet-powered car, a third entry in addition to those driven by the team's full-time 2020 IndyCar drivers Patricio O'Ward and Oliver Askew, will hit the track for the first time in the Indy 500 open test on April 30.
The car will be engineered by Craig Hampson, Arrow McLaren SP's full-time R&D engineer.
"I am a racer and the Indy 500 is the greatest race in the world," said Alonso, the 2005 and 2006 F1 world champion.
"I love the incredible fans who make it so special for all of us drivers and make me want to come back.
"I have maximum respect for this race and everyone who competes in it and all I want to do is race against them and give my best, as always."
It was revealed in January that Alonso no longer held an ambassadorial role at McLaren, but the Spaniard will now race with the team - which is returning to IndyCar after buying into the Arrow Schmidt Peterson Motorsports team - that he spent two spells with in F1 once more.
His most recent Indianapolis 500 attempt was also made with McLaren last year, though he failed to qualify for the race.
"It was important for me to explore my options for this race but Arrow McLaren SP has always been at the top," added Alonso.
"I have a special relationship with McLaren; we've been through a lot together and that creates a bond, a loyalty that is strong.
"But more than that I am impressed with how the new organisation and operation is developing into a strong package with the Chevrolet partnership.
"The team has experienced, well-qualified people and great resources, and I'm confident we can be competitive."
Team co-owner Sam Schmidt, who last month said the Indy 500 'deserves and needs' Alonso, added: "Adding Fernando to the team brings a level of experience and expertise that will benefit our two young talented full-time drivers Oliver and Pato [O'Ward].
"We have fast cars at Indy and fully believe he has the talent to run at the front, not just participate.
"That, combined with Chevrolet power and the experience of the team, will make this trio of drivers one of the strongest in the field."
McLaren Racing CEO Zak Brown added: "We've always said we're open to running Fernando in a third car for the 500, so we're delighted he's decided to join us.
"Fernando is one of the greatest drivers in the sport and it's fantastic to have him as part of the team."