The team, who have made mainly cosmetic changes to the car, have tempted driver Felipe Massa to come out of retirement after Valtteri Bottas joined Mercedes.
Massa is joined by Canadian rookie Lance Stroll, 18, son of billionaire businessman Lawrence Stroll.
Williams will be looking to reassert themselves after finishing fifth in the constructors' table last season.
"Although cosmetically the 2017 cars will look very different to their 2016 predecessors, the core of the car, the power unit and the areas situated around the power unit, have not changed a great deal," Williams said in a statement.
The new car will take to the track for the first time during a pre-season test, which will start with Brazilian Massa driving it in Spain on Monday, 27 February.
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BBC Sport chief F1 writer Andrew Benson
The challenge for Williams this year is to at least hold on to their fifth place in the constructors' championship, and try to ensure they don't slip back further after falling two places in 2016.
The new car looks clean enough but it appears among the more conservative so far. The rear packaging, for example, is nowhere near as tight and sophisticated as that on the Mercedes, with which the Williams shares an engine.
The driver line-up, too, raises questions.
Felipe Massa was tempted back out of retirement to replace Mercedes-bound Valtteri Bottas. There is no question over his motivation - he didn't really want to retire. But he gives away some performance to the best.
And Lance Stroll is an unknown quantity. European Formula Three champion and bringing millions to Williams through billionaire father Lawrence, but with an awful lot to prove.
Williams have launched their new car for 2017 in low-key fashion before pre-season testing in Barcelona.