Williams and Mercedes will continue their engine partnership until the end of 2025 after a long-term deal was announced on Friday.
Mercedes has powered Williams since 2014, a move which initially saw the Grove squad propelled into leading contention in F1, finishing that season third in the constructors' championship, over 100 points ahead of Ferrari.
Things have gone backwards for the team since, however, and they are set to finish bottom of the standings for a second straight season in 2019, with just a single point to their name though 14 races.
Reports earlier this year suggested that Williams may seek a move to Renault's supply, but deputy team principal Claire Williams shot down those rumours.
The announcement of Mercedes and Williams' long-term agreement signals the Silver Arrows commitment to F1 beyond the end of the Concorde Agreement, with Toto Wolff have previously hinted at a waiting game to see Liberty Media's 2021 regulations before committing to the sport.
Wolff said: "Williams is one of the iconic brands in Formula One and we at Mercedes are proud to count them as part of our motorsport family.
"They have been through some tough times recently but that has only served to demonstrate their resilience and strength of character as they battle back to where they belong on the grid.
"I am certain that the outlook for independent teams is bright under the financial regulations that will be introduced from 2021 and we are delighted to continue our partnership with Williams into that new era of our sport."
Claire Williams added: "Mercedes-Benz has been one of the sport's most successful engine suppliers and we believe that they will continue to have an extremely competitive engine package going forwards."
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