Robert Kubica says securing a Formula One return with Williams next year is one of the greatest achievements of his life after such a "challenging journey".

The 33-year-old Pole has not raced in F1 since 2010 due to the life-changing injuries he sustained in a rally crash seven years ago.

Kubica will be back at the highest level in 2019, though, after he was confirmed as rookie George Russell's team-mate on Thursday.

The former Sauber and Renault driver has been reserve and development driver for Williams this season after impressing during testing in 2017 and is determined to grasp his opportunity next year.

"Firstly, I would like to thank everyone who has helped me during what was a difficult period of my life over these last few years," said Kubica.

"It has been a challenging journey to make it back to the Formula One grid, but what seemed almost impossible is now beginning to feel possible, as I am excited to be able to say that I will be on the Formula One grid in 2019.

"For sure, it has been a long road to get to this point, but as that challenge now comes to an end with this announcement, a new challenge begins working with Williams on track.

"It will not be easy, but with hard work and dedication, both George and myself will work together to try and help the team get in better shape to move further up the grid.

"This year has been tough, but I have learnt a lot, and I'd like to thank Sir Frank and Claire for this opportunity.

"Being back on the F1 grid next season will be one of the greatest achievements of my life, and I'm sure with hard work and commitment we will be able to help motivate the team to achieve good things together."