Alexander Rossi is to make his Formula 1 race debut for Manor after signing a deal to compete in five grands prix for the team this year.
After a day of intense speculation about the American, the Manor team confirmed on Wednesday night that Rossi will be joining the outfit.
"We are delighted to sign Alexander as race driver," said team boss John Booth.
"He is widely-regarded as a driver who is on the cusp of an exciting F1 career and his current form in the GP2 Series has done much to reinforce his clear potential."
Rossi will take the place of Roberto Merhi in Singapore, Japan, the USA, Mexico and Brazil.
But, due to his commitments in GP2, where he is battling for the championship, he will miss the grands prix in Russia and Abu Dhabi.
Merhi will race in those events instead.
Speaking about his graduation, Rossi said: "I'm very thankful to race for the Manor Marussia F1 team and for their continued belief in me. I've been prepared for this opportunity for quite a while now.
"Many will know from 2014 that the team and I already have a strong relationship and there's a bit of unfinished business for me here.
"This is a small F1 team that has been through so much. They exemplify passion and true strength of character, and their comeback this season is extraordinary. I'm honoured to be part of this legacy and their continued growth and success."
Rossi is no stranger to F1 machinery, having taking part in free practice sessions for Caterham and Marussia in recent years.
Booth added: "Signing Alexander is a continuation of our proud record of providing young drivers with the opportunity to showcase their talents.
"We believe he will do a great job and look forward to seeing him race for the first time this weekend in Singapore.
"It is also fantastic news for the sport that it will have an American driver again, particularly with the United States Grand Prix on our horizon and now two races in South America, in Mexico and Brazil.
"I know Alexander is very excited about that and we look forward to providing him with the opportunity to show the American public what he can do.
"While Roberto is obviously disappointed, he understands that this decision is in the long-term interests of the team and we thank him for his professionalism.
"No decision has been made regarding our 2016 driver line-up and we will continue to evaluate our options during the remainder of the season."