Eight-time grand prix winner Ricciardo raced for the team between 2014 and 2018, scoring seven of his eight wins for the team and twice finishing third in the world championship.
After his exit from McLaren was confirmed back in August, he was left without a full-time seat on the grid for next season.
He will assist Red Bull with testing and simulator work, as well as commercial activity.
Ricciardo said: “The smile says it all, I’m truly excited to be coming back home to Oracle Red Bull Racing as their Third Driver in 2023.
“I already have so many fond memories of my time here, but the welcome from Christian, Dr Marko and the entire team is something I’m sincerely appreciative of.
“For me personally, the ability to contribute to and be surrounded by the best team in F1 is hugely appealing, whilst also giving me some time to recharge and refocus.
“I can’t wait to be with the team and support with simulator work, testing sessions and commercial activities. Let’s go!”
Over the Abu Dhabi Grand Prix weekend, the Australian said becoming Red Bull's third driver in Formula 1 next year beat chasing a race seat elsewhere because he wanted a year away from competition.
He reckoned that stepping away from the intensity of a racing season would also allow him to better understand if he had the motivation to want to return in 2024.
Team principal Christian Horner said: “It is great to bring Daniel back into the Red Bull family. He has enormous talent and such a brilliant character; I know the whole factory is excited to be welcoming him home.
“In his role as test and third driver, Daniel will give us the chance to diversify, assisting in the development of the car, aiding the Team with his experience and knowledge of what it takes to succeed in F1.
“We’re very pleased to be working with Daniel again and look forward to everything he will bring to the Team in 2023.”
A move to Red Bull for Ricciardo marks a reunion with the team whose young driver programme he represented through the junior ranks.
After half a season with the backmarker HRT squad in 2011, Ricciardo linked up with Toro Rosso, Red Bull’s F1 B-team, for 2012 before getting the nod to replace Mark Webber as the senior squad from 2014.
Ricciardo defeated reigning world champion teammate Sebastian Vettel in their only season together at Red Bull, scoring wins in Canada, Hungary and Belgium. Vettel left at the end of the 2014 to be replaced by Daniil Kvyat, who lasted until four races into the 2016 campaign before being replaced by Max Verstappen.
Further wins with Red Bull followed for Ricciardo in Malaysia in 2016 and Azerbaijan in 2017 before signing off from the team with victories in China and Monaco in 2018.
He then jumped ship to Renault, later revealing it felt like Red Bull had gravitated towards being Verstappen’s team. A two-year stint followed with the French manufacturer before he joined McLaren, enduring a tricky couple of seasons with the exception of his win at Monza last year.
