De Ferran was a double Champ Car champion in 2000 and 2001, representing Team Penske, and the French-born Brazilian won the 2003 Indianapolis 500 - one of the storied races that makes up motorsport's "triple crown".
He also set the world closed-course speed record, steering to a staggering lap averaging 241.428mph in 2000 at California's Fontana Speedway, during CART qualifying.
More than the sum of his achievements on-track, de Ferran was held in the highest regard throughout motor racing as a warm, friendly person, with time for everybody.
De Ferran also had a key role in Extreme E, as Co-founder, and held Sporting Director and consultancy roles at McLaren Racing.
Zak Brown, CEO, McLaren Racing and a close, long-time friend of de Ferran said: “The news of Gil's passing leaves us devastated. Gil was not only a dear friend but a fearless racer whose passion and determination on the track inspired us all.
"I’ve raced with Gil all over the world and watched him win some of the biggest races. His time with us here at McLaren Racing has been pivotal in our forward development, particularly this past year and the turnaround of our F1 team's performance and results. His legacy will continue to shape our team's future."
De Ferran's former team boss and good friend Roger Penske said: "We are terribly saddened to hear about today's tragic passing of Gil de Ferran. Our thoughts and prayers go out to Angela, Anna, Luke and the entire de Ferran family.
"Gil defined class as a driver and as a gentleman. As an IndyCar champion and an Indianapolis 500 winner, Gil accomplished so much during his career, both on and off the track.
"Gil was beloved by so many. He was a great friend to Team Penske and the IndyCar family, as well as the entire international motorsport community. Gil's passing is a terrible loss and he will be deeply missed."
Formula E Founder and Chairman and Extreme E founder Alejandro Agag said: "I am heartbroken today by the news of the passing of my dear friend and Co-founder of Extreme E Gil de Ferran.
"Rest in peace my brother. Your memory and your legacy will always be with us. This is a sad day for the world of motorsport, which has lost a hero."
Double Formula 1 champion and friend Fernando Alonso said: "I'm at a loss for words. It's a very sad day. Thank you for the moments we shared, for wholeheartedly teaching me how to race on ovals, and for the countless memories we created together. We will miss you, Gil."
The thoughts of the Formula E family are with Gil's family, friends and loved ones.