The auto, which features the new, mandatory halo device, is styled nearly identically livery-wise to the last four years with Williams' now trademark Martini branding.
"We would only put talented drivers in our auto", deputy team principal Claire Williams told reporters when questioned at a team launch.
"Sergey has impressed the technical team and it is great for us to be able to give him the opportunity to step up into a race seat".
"Overall, the philosophy we are starting to see emerge is a new approach to the collaboration between aerodynamics and design to achieve the optimum working result".
"I hope we deliver a strong element of that in this auto".
Williams released a rendering of the FW41 following its season launch in London. "I would also like to thank our partners and fans for all their confidence and support".
He said Sirotkin, who first appeared on Formula One's radar when he joined Swiss-based Sauber in 2013 as a 17-year-old development driver, had served a "fantastic apprenticeship" in the junior series.
Russian newcomer Sirotkin, previously an F1 test driver for Renault, added: "I've been in the simulator regularly, going through different set-ups with the vehicle, different tracks, seat fittings and also a lot of engineering meetings and factory tours to meet everyone". Because the current regulations for F1 testing is very limited, the simulator plays a very important role and because I'm part of this project it's important for me to build up a relationship between reality and the simulator in order to use this tool as best as we can in the future.
"We also have McLaren with a different engine: they will be a threat. So while we are reluctant to say we want to come third, our fourth or fifth because we can not predict what others have done, we would like to see a lap time gain against the guys who were taking pole position a year ago".
The FW41 is the first work of new Chief Technical Officer Paddy Lowe and he is hoping for a major step-up in aerodynamic performance akin to his prior successes at McLaren and Mercedes.
"Twelve months ago nobody would say I would have different tests in 2017".
Stroll, 19, will lead Williams during his second F1 season as the incoming Sirotkin gets his first taste of grand prix racing when he makes his debut in Australia on March 25, replacing the retired Felipe Massa.