Stroll, who celebrated his 18th birthday on Saturday and is yet to obtain his road licence, will become the second youngest driver in the sport’s history when he makes his debut at the season-opening race in Australia next year.
The Canadian’s career has so far been bankrolled by his businessman father Lawrence, who is said to be worth more than $2billion after investing in fashion labels Ralph Lauren, Tommy Hilfiger and Michael Kors.
Following Max Verstappen’s controversial arrival as a 17-year-old, the sport’s governing body raised the minimum age limit of a driver to 18 last year.
“I come from money and I am not going to deny that, but I believe I earned my shot in F1 because I have won every championship that I have competed in,” Stroll, the reigning Formula Three title holder, said at Williams’ headquarters in Oxfordshire.
“Now, the FIA has put in the superlicence for just that reason so people can’t just buy their way into F1. You have to prove yourself and win in junior categories.
“I don’t want to say when exactly I will be able to show everyone that I am not just here for money because that depends on so many other things and so many details.
“But I am just going to worry about my business and I am here today, and very happy to be joining Williams and looking forward to the 2017 season.”
Stroll becomes the second youngest driver in the sport’s history since Dutchman Verstappen made his debut for Toro Rosso last year.
Verstappen has gone on to prove himself as one of the sport’s most exciting drivers, winning on his Red Bull debut in Spain earlier this season.
Stroll, who replaces the retiring Felipe Massa, will team up with Finn Valtteri Bottas after the Finnish driver committed to Williams for another term.
“I know there has been a lot of commentary about Lance’s background,” added deputy team principal Claire Williams.
“I want to make it clear that Williams has been a team which has made a statement of intent that we would not allow financial considerations to influence our driver choice and that has been the case this year.
“Money doesn’t drive performance in the cockpit - you either have the talent or you don’t - and Lance has proved that he has got that talent and has done what he has done to earn his race seat in Formula One for next year.
“He just has to do the job and he will do that in order to dispel those rumours.”