The news comes as somewhat of a surprise but the Spaniard has been told he has the full backing and support of McLaren and engine partner Honda.
Alonso will hit the speedway circuit in Indiana on Sunday, May 28 – the same day the prestigious Monte Carlo F1 race takes place.
The veteran will be racing for the Honda-powered Andretti team.
After a shaky start to the 2017 season, McLaren have yet to announce who will replace Alonso behind the F1 wheel – but there is a possibility that Jenson Button could return.
.@alo_oficial what an absolute legend. Could he win Indy 500 at first attempt? Graham Hill did it. ALO wants to win Monaco, Indy & Le Mans— Andrew Benson (@andrewbensonf1) April 12, 2017