How much the sponsorship deal is worth has not been disclosed, but it is expected to be a multimillion-pound sum. A spokesperson for WilliamsF1 would not confirm the exact length of the deal, but it is understood that AT&T have agreed a contract of at least three years.
As part of the deal, the WilliamsF1 team will be now known as AT&T WilliamsF1. It does not affect any of the existing 24 partners of WilliamsF1, which include Reuters, Bridgestone, Budweiser, Accenture and RBS.
AT&T said it would also be providing technical equipment for the team, including voice communication between driver and pit crew, data support services, and real-time data analysis.
The company has previously sponsored Jaguar Racing and McLaren, but it is the first time it has assumed a title sponsorship role.
Sir Frank Williams, team principal at WilliamsF1, said: "It is our firm commitment to represent [AT&T's] interests to the very best of our ability on the race track and assist with the communication of their service offer that we too will have the significant benefit of being able to use."
The signing of the deal follows Fernando Alonso, driving for Renault, retaining his Formula 1 world champion title at the Brazilian Grand Prix on Sunday.
The race, which was seven-times world champion Michael Schumacher's last before retirement, was won by fellow Ferrari driver Felipe Massa, making him the first Brazilian to win his home race since Ayrton Senna in 1993.
AT&T WilliamsF1 said it would unveil its traditional blue and white livery for the 2007 season in January.
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