The team, which won last year's Spanish Grand Prix, returned to the scene of Pastor Maldonado's victory to take the wraps of their 2013 car - the last to be announced by this year's Formula One competitors.
Frank Williams backs new car to challenge Formula One leaders this season
The team are the second most successful constructors in F1 history, but finished down in eighth place for last year's championship.
But with new recruit Valtteri Bottas joining Pastor Maldonado at the team, and changes made to the car - which was unveiled today at testing in Barcelona - founder Frank Williams believes they will be in a position to challenge once again.
"We will have to wait until Australia to truly see what we have, but we believe it is a step forward from last year's car which was also a very competitive vehicle," he said.
"Williams has been at the top many times over the last 30 years. It's the nature of the sport to have ups and downs, but when we are down we always fight our way back.
"I'm hoping that with the current team we have in place we will be in a position to challenge the very best."
Maldonado claimed their first victory in nearly eight years with victory in the Spanish Grand Prix last May, beating Fernando Alonso and Kimi Raikkonen at the Circuit de Catalunya where their new car was revealed.
Williams claimed more than 80 per cent of the car was new, including the gearbox and rear suspension as well as radiators, floor, exhausts, bodywork and nose - with a 'considerable' weight saving on the 2012 vehicle.
"Given the rule stability over the winter, I'm pleased with the gains that we've been able to make with this car," said Mike Coughlan, the team's technical director.
"It's a better, more refined Formula One car than the FW34."
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