Following months of growing speculation that McLaren were poised to end their near two-decade relationship with Mercedes and revive their previously all-conquering Honda partnership from the end of next season, Honda's CEO Takanobu Ito and McLaren boss Martin Whitmarsh confirmed the deal in a press conference in Japan on Thursday.
The mouthwatering tie-up is being described as a "multi-year Formula 1 technology partnership" which will see McLaren run both Honda's all-new V6 turbocharged engine and energy recovery system, the power plant already under development at the Japanese firm's R&D facility in Tochigi.
"Great to see the return of Honda to F1 with McLaren from 2015. Good news for F1 too. Will be tense between Merc and McLaren in 2014."
Sky Sports F1's Martin Brundle
Reacting to the breaking news in the UK on Thursday morning, Sky Sports F1 commentator David Croft tweeted: "Personally I think it's great for the sport that Honda are returning. With V6 units it makes sense to them now but pressure is on to deliver."
However, Whitmarsh expressed his confidence that the second incarnation of the partnership could live up to the glorious success of the first, when the two companies won four Drivers' and Constructors' Championship doubles on the spin between 1988 and 1992.
"It's fantastic news for everyone who loves Formula 1 to be able to welcome Honda back to Formula 1," said the McLaren Team Principal.
"Together, we're about to embark on a new and extremely exciting chapter in McLaren's history. Like McLaren, Honda is a company with motor racing woven into the fabric of its heritage. We're proud and thrilled to be joining forces once more to take on the world in Formula 1.
"Whilst both companies are fully aware that we're embarking on a very demanding journey together, we're hugely committed to the success of the partnership, and we'll spend the next 18 months working together to ensure that we're fully established and competitive ahead of our first grand prix together in 2015."
The announcement marks a glorious, and high-profile, return to the top level of motorsport for Honda, whose last F1 venture, then as a team owner, ended abruptly at the end of 2008 when they sold their Brackley-based outfit - which is ironically now Mercedes - to Ross Brawn in wake of plunging sales of their road cars amid the worldwide financial crisis and two years of dismal on-track underperformance.
The Japanese car maker's greatest successes in F1 have come in the guise of an engine supplier with first Williams and then McLaren and their CEO and President said they were attracted to a return by the sport's impending new greener engine rules.
"Ever since its establishment, Honda has been a company which grows by taking on challenges in racing," Takanobu Ito said.
"Honda has a long history of advancing our technologies and nurturing our people by participating in the world's most prestigious automobile racing series. The new F1 regulations with their significant environmental focus will inspire even greater development of our own advanced technologies and this is central to our participation in F1.
"We have the greatest respect for the FIA's decision to introduce these new regulations that are both highly challenging but also attractive to manufacturers that pursue environmental technologies and to Formula One Group, which has developed F1 into a high value, top car racing category supported by enthusiastic fans.
"We would like to express our sincere gratitude to Mr Jean Todt, the President of FIA and to Mr Bernie Ecclestone, the CEO of Formula One Group who showed great understanding and cooperation to help realize our participation in F1 racing."
Indeed, McLaren's press release contained words of congratulations from both Ecclestone and Todt, with the latter saying: "I am very happy to hear about Honda's important decision to return to Formula 1 with McLaren from 2015.
"The introduction of the new powertrain next year, in the form of a 1.6-litre V6 engine with direct injection and energy recovery, is a very exciting challenge and demonstrates a vision for the future of the sport.
"I am sure that Honda will become a strong contender in years to come."
The flip side of the deal means that McLaren will only run current partner, and former shareholder, Mercedes' new engines for one solitary year of F1's new V6 turbo engine regulation era, the two parties having been together since 1995.
The partnership has won three drivers' world titles, the 1998 constructors' crown and 78 races in its 19 seasons to date and Whitmarsh made clear that McLaren were focused on continuing that winning tradition during the relationship's final 18 months.
"It's appropriate to recognise that until the end of 2014 we'll maintain a full commitment to our existing and long-standing partner, Mercedes-Benz, for which we retain the utmost respect and with whom we intend to continue to work diligently and professionally," the McLaren chief added.
"McLaren-Mercedes has so far won an incredible 78 grands prix and four world championships. We aim to cap our long-standing partnership with the same ambition and resolve with which we began it: namely, to keep winning."
