Williams will become Renault's fourth formula one engine customer in 2012, the British team and the French marque announced on Monday.
Both sides said the deal covers the 2012 and 2013 seasons and possibly also 2014 and beyond when the sport switches to turbo V6s.
"We are already working on an extension for the new engine formula," confirmed Williams chief executive Adam Parr.
Williams, struggling this season with Cosworth power, won its last title with works Renault power in 1997.
"Williams has recently taken several important steps, both commercially and technically, to update its operations and we feel that this partnership is another important step in its rigorous plan," said Renault Sport F1 president Bernard Rey.