(CNN) -- After months of speculation, one of Formula One's worst kept secrets has finally been confirmed.
Fernando Alonso, the double world champion who recently left Ferrari, will rejoin McLaren for the 2015 season, which gets underway in March.
The Spaniard, who won back-to-back world titles with Renault in 2005 and 2006, joins the British team after ending his four-year association with Ferrari.
He will be partnered by Jenson Button, whose services were retained above Kevin Magnussen, who stays on as a test and reserve driver.
Between them, Alonso and Button have won three world titles, 47 grands prix and achieved 147 podium finishes from a combined 500 races.
Now 33, Alonso will be expected to boost McLaren's fortunes after a season which saw it struggle to match the pace set by the all-conquering Mercedes team.
"Over the past year I have received several offers, some of them really tempting given the current performance of some of the teams that showed interest," he said in a statement.
"But, more than a year ago, McLaren-Honda contacted me and asked me to take part, in a very active way, in the return of their partnership -- a partnership that dominated the Formula 1 scene for so long."
Between 1988 and 1992, McLaren and Honda won 44 grands prix out of 80, with Ayrton Senna and Alain Prost winning all but one of the 16 races in one season.
"I still remember, as a kid, the posters in my wardrobe, my toy cars in which I dreamed I would one day emulate Ayrton, and the kart that my father built for my older sister, and that I ended up falling in love with," Alonso added.
"That kart had the livery of one of the most legendary partnerships in the history of Formula 1, McLaren-Honda, the car that Ayrton drove, the same partnership to which I am now honored to join.
"I am joining this project with enormous enthusiasm and determination, knowing that it may require some time to achieve the results we are aiming for, which is no problem for me."
It remains to be seen whether McLaren's new engine partnership with Honda returns it to the top of the sport.
Alonso previously joined McLaren in 2007, but left after just one season due to tensions between him and then rookie teammate Lewis Hamilton -- the now Mercedes driver who was crowned 2014 world champion last month.
This time around, Alonso will be paired with the vastly experienced Button.
The Briton, who won the 2009 drivers' title with Brawn, has signed a new deal to extend his four-year stay with the team.
"I am extremely excited to be embarking on my 16th year in Formula 1 and my sixth season for McLaren," said the 34-year-old, whose future had been heavily debated in recent days.
"Like Fernando, I am certain that McLaren and Honda will achieve great things together, and I feel sure that, working together, all of us will pull incredibly hard to create a brilliantly effective winning team.
"I admired Ayrton Senna enormously, but, for me, it was the exploits of Alain Prost that inspired me most as a boy.
'The best driver lineup'
"The way he stroked those beautifully brutal red-and-white cars to grand prix wins and world championships was to my mind poetry in motion, and I have tried to emulate his driving style ever since.
"Being a part of new-look McLaren-Honda is a wonderful opportunity for all of us and I am very pleased to have been invited to do my bit. In fact, I am absolutely raring to go."
"I am sure (Fernando and I) will work extremely well together."
After plenty of uncertainty over whether Button or Magnussen would be retained for 2015, McLaren chairman and CEO Ron Dennis is delighted with the pairing of two former world champions.
"I can safely say that we now have by an order of magnitude the best driver lineup of any current Formula 1 team," he said.
"We signed Fernando a little ago, but we decided not to announce the fact until we had also re-signed Jenson as his teammate. For many reasons, our negotiations with Jenson took quite a long time."
The decision to retain Button means Magnussen loses his seat after just one season in the sport.
The Dane finished 71 points behind Button in this year's championship.
"I am very glad that Kevin will remain part of the team," said Button. "He is a very quick driver and a really nice guy."