Williams test driver Susie Wolff's dream of becoming the first woman to race in Formula 1 for 40 years is over as she has announced she is to retire from motorsport.

The Oban born driver - the wife of Mercedes boss Toto, became the first woman to take part in an F1 race weekend in a quarter of a century with a debut Practice One outing at last year's British GP.

After being promoted to Williams' test driver for 2015, Wolff took part in four Friday practice sessions this season, the last of which was at Silverstone in July.

Now she believes her aim of racing in Formula 1 "isn't going to happen".

"I got so close and I fought hard. But my gut feeling tells me it is time to move on to explore new challenges," Wolff, 32, said.

She was disappointed when overlooked in March when Williams hired former Sauber driver Adrian Sutil as reserve when Valtteri Bottas suffered a back injury which ruled him out of the Australian GP.

"I am now closing this chapter but looking forward to new challenges in the future," said Wolff, who spent seven years racing in the DTM for Mercedes before switching focus to F1.

"I'd like to thank Williams for the opportunity they have given me over the last few years which has allowed me to achieve my dream of driving a Formula 1 car.

"It has been great to work with everyone at the team, both at Grove and trackside, and I'd like to thank everyone who has been part of my journey at Williams."

Wolff will make her final appearance as a racing driver in the Race of Champions, which takes place in London's Olympic Stadium on 20-21 November.

Williams deputy team principal Claire Williams added: "It has been a pleasure to work with Susie over the years and see her develop as a driver within the team.

"Her feedback and knowledge of the car has been an important part our recent development and we will be sorry to see her go.

"We want to thank her for all her efforts and wish her the very best for her future endeavours.

"We will of course be supporting both Susie and Felipe [Massa] at the Race of Champions, and hope Susie has a great weekend to mark the last time we see her race."