Williams will use Mercedes engines in Formula 1 at least until 2025.
The team, already committed to Mercedes for next season, have signed a new agreement for the following five years.
Williams have declined in form since finishing third in 2014 and 2015, their first two seasons with Mercedes after turbo-hybrid engines came into F1.
They finished last in 2018 and are on course for the same position this year, but they hope a technical department restructure will revive fortunes.
Williams deputy team principal Claire Williams said: “Mercedes has been one of the sport’s most successful engine suppliers and we believe they will continue to have an extremely competitive engine package going forwards.
“Over our time with them they have become a real friend of the team.” — BBC.