Williams have signed outgoing Ferrari driver Carlos Sainz for the 2025 Formula 1 season on a two-year deal.
Sainz has been seeking a 2025 seat since Ferrari announced in February that they were replacing him with Lewis Hamilton next year.
With ambitious Williams having made a major push to sign the three-time race winner to partner Alex Albon, the Grove-based team have beaten Alpine and Sauber to Sainz's signature with the Spaniard agreeing a deal for the 2025 and 2026 seasons - with "options to extend" beyond that.
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He will replace American Logan Sargeant as Albon's team-mate in what will be one of F1's strongest driver line-ups.
Williams boss James Vowles described the signing of Sainz as a "strong statement of intent".
"I am very happy to announce that I will be joining Williams Racing from 2025 onwards," said Sainz, who has been at Ferrari since 2021.
"It is no secret that this year's driver market has been exceptionally complex for various reasons and that it has taken me some time to announce my decision.
"However, I am fully confident that Williams is the right place for me to continue my F1 journey and I am extremely proud of joining such a historic and successful team, where many of my childhood heroes drove in the past and made their mark on our sport.
"The ultimate goal of bringing Williams back to where it belongs, at the front of the grid, is a challenge that I embrace with excitement and positivity. I am convinced that this team has all the right ingredients to make history again and starting on January 1 I will give my absolute best to drive Williams forward alongside every single member of the team."
Sainz was seen as a candidate to take Hamilton's seat at Mercedes and was also linked with Red Bull, before ultimately appearing to be left with a choice between Alpine, Williams or the Sauber team that will become Audi in 2026.
'Sainz-Williams fit is perfect' - Vowles pulls off driver coup
Sainz's has regularly been described in recent months as a 'cork in the bottle' for the rest of the driver market as the 29-year-old carefully weighed up his options and offers over where to drive in 2025.
Although the Spaniard had originally targeted another front-running seat to replace the one he currently holds at Ferrari, it quickly became clear that ambition was unlikely to be realised for next season.
Red Bull was not an option for him, while Mercedes was more likely to promote their teenage protege Andrea Kimi Antonelli to Hamilton's seat if they could not make an audacious swoop for Max Verstappen happen for at least next year.
But given his pedigree and reputation as one of F1's most-consistent and intelligent performers over 10 seasons in F1, Sainz emerged as a major target for several teams further down the grid with ambitions to improve their fortunes.
Indeed, in an unusually frank public admission at June's Spanish GP, Sainz's home race, Williams team boss Vowles declared that Sainz was his "number one target" to partner Albon.
And despite long-standing interest from Audi and a late renewed push from Alpine, Vowles has now got his man in what represents an undoubted show of faith in Williams from their new star signing.
"Carlos joining Williams is a strong statement of intent from both parties," said the Williams team principal.
"Carlos has demonstrated time and again that he is one of the most talented drivers on the grid, with race-winning pedigree, and this underlines the upwards trajectory we are on.
"Carlos brings not just experience and performance, but also a fierce drive to extract every millisecond out of the team and car; the fit is perfect.
"In Alex and Carlos we will have one of the most formidable driver line-ups on the grid and with huge experience to guide us into the new regulations in 2026."
What's the significance of the Sainz signing and can he help propel Williams back up the grid?
The highly-regarded Vowles, who was previously strategy director at Mercedes, is in his second year in charge at the legendary team which won nine constructors' titles in a period of F1 domination through the 1980s and 1990s, but since fallen onto far fallower times over the past two decades.
Having finished 10th and last in the standings in four of the five seasons prior to Vowles' arrival, Williams enjoyed their best season since 2017 to finish seventh last year - although they sit only ninth so far after 14 races in 2024, between Alpine and Sauber, with four points.
However, Vowles has repeatedly insisted that it is the work and investment taking place behind the scenes to modernise the team's working practises and infrastructure which is the main priority for the coming seasons and will ultimately transform them back into front-runners.
And having already tied down former Red Bull driver Albon to a new "multi-year term" in May, the arrival of Sainz underlines that Williams mean business - even if it also inevitably means that pressure will eventually ramp up on them to provide the stellar pairing with a car to challenge.
The team's most realistic next chance to make that jump back up the order on the track will be the next major regulation change in 2026, when the sport's chassis and engine rules are being overhauled.
Significantly, Williams will continue to be powered into the new era by engines from Mercedes, who are strongly tipped to produce one of the best power units, just as they did when the current hybrid-turbos were introduced in 2014.
"[The drivers'] belief in this organisation's mission demonstrates the magnitude of the work going on behind the scenes," added Vowles.
"People should be in no doubt about our ambition and momentum as we continue our journey back to competitiveness - we are here, we are serious and with Dorilton's backing we are investing in what it takes to return to the front of the grid.
Sainz, who will now race for his fifth different team in F1 since joining the grid nine years ago at Toro Rosso, added: "I want to thank James Vowles and the entire board of Williams for their trust and determination. Their solid leadership and convictions have played an important role in my decision-making."
Slater: Vote of confidence in Williams, vote of no confidence in Sauber
Sky Sports News' Craig Slater...
"Sainz had certainly been holding out hope to drive for Red Bull next year for a couple of months.
"It became clear that was not an option. I think the decision to sign for Williams is a great vote of confidence in the improvement they are making and the leadership of James Vowles.
"It is a vote of no confidence in the Sauber project. This was meant to be a big outfit coming into F1 with a lot of money to win races.
"They really do not look like they are making process.
"One insider in that team described the situation as a mess and observed that they couldn't out a wheel properly on a car this season, nevermind be in a position for the championship.
"Because none of the obvious top seats came open to Sainz, he has decided he needs to make a decision or risk losing the Williams seat.
"I think it is a fantastic combination, him and Alex Albon.
"I think the question is will Red Bull ultimately live to regret sticking with Sergio Perez when other options are out there."
What now for the rest of the 2025 driver market?
With the Sainz-shaped cork finally out of the driver market bottle, the rest of the pieces on next season's grid may now swiftly fall into place.
Having missed out on the Spaniard, Alpine and Sauber now must turn to alternative options for their one respective open seat.
At Alpine, reserve driver Jack Doohan appears the clear favourite to partner Pierre Gasly, while incumbent Valtteri Bottas may ultimately earn a reprieve at Sauber-Audi next to new arrival Nico Hulkenberg.
Mercedes, meanwhile, seem increasingly certain to promote Antonelli.
Officially there are only four seats left open on the 2025 grid, although the situation at Red Bull potentially remains fluid with Sergio Perez's future at their senior team in growing doubt amid a sustained poor run of form.
RB's Daniel Ricciardo - who does not possess a 2025 contract at all yet - and Yuki Tsunoda are options to replace the struggling Perez were Red Bull, whose bosses met to discuss the driver situation on Monday, to make a change, with reserve Liam Lawson also in frame for a promotion at either outfit.
Were Lawson to miss out completely on a Red Bull-owned seat for next season, the highly-regarded New Zealander could also come into play for other teams elsewhere too.
Formula 1 returns after the summer break with the Dutch Grand Prix at Zandvoort on August 23-25, live on Sky Sports F1. Stream every F1 race and more with a NOW Sports Month Membership - No contract, cancel anytime