The Australian will replace Carlos Sainz, whose departure for Ferrari will be confirmed in parallel, the Spaniard replacing Sebastian Vettel.
The two drivers will reach the end of their initial two-year agreements at the end of the 2020 season, although McLaren has had an option on Sainz for a third year.
Ricciardo almost joined McLaren as he considered his options while he was still discussing a contract extension with Red Bull in the summer of 2018. Eventually, he decided to go to Renault instead, while ” in turn Sainz left the French manufacturer to join McLaren.
Ricciardo’s move to McLaren – which will get Mercedes-Benz engines next year – opens a headquarters at Renault alongside Esteban Ocon, who has an agreement that will end in late 2021.
Fernando Alonso is said to have expressed interest in returning to the Enstone team for a third stint.
Speaking to Sky F1 last week, Renault boss Cyril Abiteboul said he hoped to keep Ricciardo, but hinted that there were no guarantees.
“We love Daniel,” he said. “Daniel embarked on a project, which was very clear from day one, and this project is clearly incomplete, both at the team level and I also assume at the Daniel level.
“In particular, the circumstances are very strange since the season has not even started, so we are literally halfway through what we need to do together, and we must already be thinking about the future.
“I like to think that we can do more together, accomplish more together and get more results than we have done so far. This is clearly the intention.
“Having said that, we have a strategic plan, this plan included substantial investments for the 2021 car. It turns out that it is 2022 because the rules are delayed by a year, that does not mean that we are dropping what we have to do this year and next year before 2022.
“We would like Daniel to be part of this construction, but we clearly know that we have to focus on what is missing so far in the team, and what is missing is not the pace of the drivers. “