The defender joined the Blues from the New York Red Bulls at the end of the January 2016 window, but only has made a pair of Premier League appearances with the London club.
Though he got those early opportunities, Miazga was never a part of Antonio Conte's plans when the manager arrived in the summer of 2016 and spent the next two seasons on loan with Vitesse of the Eredivisie.
Miazga became a key member of the Eredivisie's side backline over that span, playing 72 games and helping the club qualify for the Europa League in both seasons.
The centre-back also as emerged as an important figure in the U.S. national team's set up in 2018, as the program looks to rebuild with a youthful core after their failed World Cup qualification campaign.
The 23-year-old will now test himself in Ligue 1 with Nantes, who finished ninth last season after a tough start to 2018.
Miazga also signed a new contract with Chelsea, which will tie him down to the Blues until 2022.
However, the loan includes a purchase option for Nantes that can be exercised at the end of the season.
— FC Nantes (@FCNantes) August 6, 2018
Un parfum d'Amérique est de retour à Nantes... pic.twitter.com/whRntmEf4J
He will be the second USMNT player to feature for the club after international team-mate Alejandro Bedoya, who appeared for Nantes 87 times over the course of three Ligue 1 seasons between 2013-2016.
Nantes open up their Ligue 1 campaign at home against Monaco on Saturday.