The 28-year-old Finn, who since joining Mercedes at the beginning of 2017 has scored three Grand Prix victories and five pole positions, has signed a one-year contract extension, with an option for a further year in 2020.
“It is great news that I will be racing for Mercedes in 2019 and it is nice to announce it here in Hockenheim - not just the home race for Mercedes but also the circuit where I took my first ever single-seater wins back in 2007," said Bottas.
"This year, with a full winter of preparation, I have been able to make a good step forward - and I believe that there is still more to come. We have not been so lucky in the races this year but the team knows how I am performing, and this is a great sign of confidence in me and my driving.
"I enjoy working with the team, and also being team-mates with Lewis - we have a good relationship, honest and straightforward, and always aiming to get the right results for Mercedes.
"We have a big battle on our hands right now, so it's good to have the future clear for everybody - it means we can have a full focus on the championship fight.
"Obviously, my goal is to keep performing at a high level - and to make it a no-brainer for the team when it comes to deciding their plans for 2020 as well."
Team chief Toto Wolff praised the on-track abilities of Bottas, who lies fifth in the driver standings afer four podium finishes so far this season, but also stressed the importance of his working relationship with reigning champion team mate Hamilton.
"Valtteri's performances have been excellent this season and, if not for our mistakes and his misfortune, he could be leading the drivers' championship at the moment," said Wolff.
"When we took the decision in favour of Valtteri for 2019, it wasn't just about his undoubted speed and work ethic, but also a question of character. His relationship with the team, including Lewis, is open and trusting, without any politics at all.
"Those are the ingredients you need when you're fighting strong rivals in both championships and they mirror the values inside the team. I am very excited to keep Valtteri in the team and look forward to celebrating many more successes with him."
Jonny Reynolds [Editor in Chief, F1.com] says:
Having inked Lewis Hamilton to a two-year deal, it was no surprise to see Mercedes extend their partnership with Bottas, with all parties having indicated for some time that they’d like to continue what has been a very positive relationship to date.
The popular Finn has slotted in seamlessly at the Silver Arrows since his transfer across from Williams prior to last season, forming a positive working relationship with Hamilton and proving an excellent foil for the Briton.
Indeed, the 28-year-old has been one of 2018’s quickest and most consistent performers, and can count himself extremely unlucky to be only fifth in the world championship standings after 10 races.
No one has scored more than Hamilton’s seven podiums this season, but with a fairer wind Bottas would have the same number – plus at least one victory to his name.
Think back to Azerbaijan when a superbly judged drive should have resulted in a fourth career victory, only for a blown tyre to wreck his chances almost within sight of the flag. Then there was France where, having qualified alongside Hamilton on the front row of the grid, he was unceremoniously tipped down the order by Sebastian Vettel at the first corner.
And only a few weeks ago in Austria another podium shot was lost when a hydraulics issues forced him to retire from second place – that after he’d captured a superb pole position.
Such knocks might rattle other drivers, but Bottas is ingrained with a seriously steely determination. You get the sense there’s much more to come from the Finn – and so, clearly, do Mercedes.