Williams will be the fourth team on the grid in 2014 to run with the German marque's engines alongside McLaren, Force India and the works squad.
Wolff is confident the Williams-Mercedes partnership will be successful and hinted that a fourth engine partner was still possible, with Lotus known to have held talks about a possible contract.
"The proud heritage of Williams and the company's commitment to technological excellence make it a perfect long term partner for Mercedes-Benz under the new powertrain regulations," said Wolff.
"It is a win-win situation for both HPP [Mercedes-Benz High Performance Powertrains] and Williams, which will ensure HPP is able to supply at least three teams on a long term basis under the new regulations and could open interesting new perspectives for technology transfer.
"We look forward to enjoying much success together over the coming years."
The deal also ensures that Mercedes will have at least three teams running its engines in 2015, when long-time partner McLaren switches to Honda powerplants.
"A further positive is that this new agreement provides Mercedes-Benz with the long term stability of supplying our works team and at least two partners from the 2015 season onwards, following the conclusion our relationship with McLaren at the end of next season," said Andy Cowell, managing director of Mercedes AMG HPP.
Renault, which has supplied Williams with engines since the start of last season, has passed on its thanks and guaranteed that it will continue to push to the end of the season.
"We would like to thank Williams for the warmth it has extended to Renault over the last two years and wish the team the very best for the future," said Renault Sport F1 president Jean-Michel Jalinier.
"Williams and Renault have a long history together and quickly recaptured its winning spirit in the early days of the rekindled partnership with victory in Spain 2012.
"We will continue to actively work with the team until the Brazilian Grand Prix in November to end the second incarnation of the partnership with results that do justice to its reputation."