The 25-year-old returns to Ligue 1 just two years on from a reported £40 million ($73 million) move from the Principality club.

Monaco has the option to sign Bakayoko on a permanent deal, with the prospective fee reportedly set at £38 million ($69.4 million)).

"I am very happy to come back to AS Monaco, a club with which I keep fantastic memories," he said.

"Since 2017, I had the opportunity to have two very good experiences with Chelsea and [AC] Milan.

"I hope to be able to integrate as quickly as possible in this collective, in an environment that I already know, and especially with the desire to bring to the group what I know how to make a good season."

Vice president Oleg Petrov said: "We are delighted to welcome Tiemoue Bakayoko to AS Monaco.

"Tiemoue has demonstrated his quality at the highest level in France but also in England and Italy. He returns to a club and a championship that he knows well. His qualities and experience are additional assets for the team."

Bakayoko made 43 appearances in all competitions under Antonio Conte in 2017-2018, including in the FA Cup final win over Manchester United.

However, he was considered expendable by Maurizio Sarri and spent last season on loan with AC Milan.

Head coach Frank Lampard said on Sunday (AEST) that the France international was due to head out on a temporary deal "to try to bring himself back to where he wants to be".

Bakayoko played a key role in Monaco's hugely successful 2016-2017 season, in which it won Ligue 1 and reached the semi-finals of the UEFA Champions League.

The club encouraged Kylian Mbappe and Benjamin Mendy to follow suit and return to Stade Louis II by posting a cheeky tweet as it announced Bakayoko's arrival.

Monaco had earlier confirmed that Adama Traore has joined Metz on loan for the remainder of the season.