Brazilian Bruno Senna has signed to drive for Williams in 2012.
The move means the 28-year-old is joining the team for which his uncle Ayrton Senna was driving when he was killed in 1994.
He was preferred to veteran countryman Rubens Barrichello for the position and will partner Venezuelan Pastor Maldonado.
Senna impressed sporadically after being drafted in by the Renault team in the final races of last season.
His only other experience of F1 is spending the 2010 season with the struggling HRT team.
"I feel very privileged Williams has selected me as one of their race drivers," said Senna, who will make his debut for Williams in Jerez, Spain on 9 February in the first of the team's winter tests.
"The team has a great heritage and I hope I can help write a good chapter in their history.
Williams are taking a significant risk in employing Bruno Senna alongside Pastor Maldonado in 2012. It is a crucial season for the team that dominated F1 for large parts of the 1980s and 1990s. Williams suffered the worst season in their history last year and they need to prove that a major restructure has put them back on the right track. Some may see the move as driven by a desire for sponsorship income but while Senna has undoubted potential Williams need him to deliver on the track fast - and often. That's why many in F1 will believe they might have been better going for a proven driver such as Rubens Barrichello, who can be relied upon to deliver consistent results.
"The evaluation process has been intense and methodical, but the time I have spent in the factory has demonstrated the team has great people and all the resources needed to achieve better things this season.
"It will be very interesting to drive for a team that my uncle has driven for, particularly as quite a few of the people here actually worked with Ayrton.
"Hopefully we can bring back some memories and create some great new ones too."
Asked about how he copes with carrying on the Senna legacy in F1, Bruno told
Radio 5 live
: "It's something that's been present for me since my first race, and I have learned how to deal with the memories I bring of Ayrton.
"It's very good for me to bring back memories of Ayrton in people. People are very fond of Ayrton and I am in no way trying to take his spotlight.
"It brings me a great feeling, and I'm sure it's going to be more special every day."
Barrichello, who will be 40 this year, had been hoping to extend his F1 career into a 20th season but Williams preferred to go for the promise and potential of Senna rather than Barrichello's proven pace and experience.
There was support among some sections of the Williams team for Barrichello keeping the drive, on the basis that he is a proven talent and because of his renowned technical expertise.
Williams had the worst season in their history in 2011 and are in the middle of a rebuilding process, with a new technical director, chief aerodynamicist and chief engineer, and some in the team felt they could benefit from the continuity and experience Barrichello would have brought.
However, sources close to Williams say the relationship between driver and management soured as a result of the slide in the team's results.
Team owner Frank Williams said: "The circumstances of Bruno's two seasons in Formula One have not given him an ideal opportunity to deliver consistently.
"So it was essential we spent as much time with him as possible to understand and evaluate him as a driver.
"We have done this both on track and in our simulator and he has proven quick, technically insightful and above all capable of learning and applying his learning quickly and consistently.
"Now we are looking forward to seeing that talent in our race car."
The only remaining free seat in F1 for 2012 is the second HRT alongside veteran Spaniard Pedro de la Rosa.
But Barrichello is considered unlikely to want to drive for the back-of-the-grid Spanish team.
Veteran Italian Jarno Trulli's tenure at Caterham - who raced as Lotus last year - is also believed to be insecure, but Russian Vitaly Petrov, who drove for Renault in 2010 and 2011, is tipped to get that seat.