Spaniard Alonso has won the first leg of the treble twice at the Monaco Grand Prix and added the 24 Hours of Le Mans title earlier this year
Fernando Alonso will bid to become only the second driver after Graham Hill to complete motor racing's Triple Crown next year at the Indianapolis 500 with McLaren, the manufacturer announced on Saturday.
Spaniard Alonso has won the first leg of the treble twice at the Monaco Grand Prix and added the 24 Hours of Le Mans title earlier this year.
The 37-year-old took part in the 2017 Indy 500, and was named Rookie of the Year despite being forced to retire with engine failure while sitting in seventh place.
"I've made clear for some time my desire to achieve the Triple Crown," said Alonso.
"I had an incredible experience at Indianapolis in 2017 and I knew in my heart of hearts I had to go back if the opportunity was there.
"It's a tough race and we'll be up against the best, so it will be a huge challenge. But we're racers and that's why we race."
The two-time Formula One world champion will retire from the sport at the end of the current season, which ends at the Abu Dhabi Grand Prix later this month.
He has endured a miserable second spell in F1 with McLaren since rejoining the team in 2015 from Ferrari, failing to post a podium finish in 76 races.
"It's a case of unfinished business for us with Fernando," admitted McLaren Racing CEO Zak Brown.
"No Indy 500 is a cakewalk, it's a massive challenge. We have the utmost respect for the race and our competitors.
"So, we are under no illusions. But McLaren are racers first and foremost, as is Fernando. We're going for it."
Alonso is currently languishing down in 10th spot in this season's Formula One drivers' standings and on Saturday was eliminated from the first session of qualifying for the Brazilian Grand Prix.
Briton Hill, also a two-time F1 world champion, sealed his Triple Crown by adding the 1972 24 Hours of Le Mans to his five Monaco Grand Prix wins and 1966 Indy 500 triumph.