Jenson Button will return to the Formula One grid for a one-off appearance at next month's Monaco Grand Prix.
Button, 37, will replace Fernando Alonso who is heading to the United States for the Indianapolis 500 which takes place on the same weekend.
The British driver, who treated last year's final race in Abu Dhabi as the last of his 17-season career, will team up with Belgian Stoffel Vandoorne for McLaren at the Monte Carlo race on 28 May.
Button remains under contract with McLaren after agreeing a two-year ambassadorial role, but he is yet to drive this year's car.
"I'm thrilled to be making a one-off return to Formula One racing, and I couldn't think of a better place to make that return than my adopted home Grand Prix of Monaco," Button said. "I've won the race before, in 2009, and it's one of my all-time favourite racetracks.
"It's a tricky street circuit on which a good driver can really make a difference and, although the McLaren-Honda hasn't begun the season well, I think it may be more suited to Monaco than to the faster circuits that Fernando and Stoffel have raced it on so far this season.
"I realise we won't have a realistic chance of repeating my 2009 victory, but I think we'll have a opportunity to score world championship points, which will be very valuable to the team in terms of constructors' rankings."
Alonso's decision to take part in the 101st Indy 500 left a vacant seat alongside Vandoorne, the Belgian who replaced Button at McLaren this season.
Button, who will start his 306th race in Monte Carlo, was the leading, and obvious, candidate to fill the void.
The Englishman is not scheduled to take part in next week's two-day test here in Bahrain, but despite his recent lack of track action he is hopeful he will prove an able substitute.
"I'm looking forward to pitting myself against the unique racing challenge that is the Monaco Grand Prix," Button, the last driver to win a race for McLaren, added.
"I'll drive the McLaren around Monaco in the simulator beforehand, and I reckon I'll be ready for the race after doing that.
"I'm supremely fit, having done a lot of triathlon training recently, so I have no worries on that score. And it'll be nice to say 'hi' to all my old Formula One mates, too, and hopefully to give the fans something to cheer about."