* Manley took over as FCA CEO in 2018 to replace Marchionne

* Manley led FCA through merger with PSA to form Stellantis

* Manley to start as AutoNation CEO on Nov. 1

Sept 21 (Reuters) - No. 1 U.S. auto retailer AutoNation Inc on Tuesday named former Fiat Chrysler (FCA) top boss Michael Manley as its new chief executive, replacing long-serving CEO Mike Jackson.

British-born Manley took over as CEO of FCA in July 2018 after long-time chief Sergio Marchionne, a charismatic and iconic figure credited with saving Fiat, fell ill and died suddenly after succumbing to complications from surgery.

Manley, 57, led FCA until January 2021, when the company merged with PSA to form Stellantis, the world's fourth-largest carmaker, a merger that he helped negotiate.

Manley, who also oversaw the successful overhaul of FCA's high-margin Jeep and RAM brands, currently serves as Head of Americas for Stellantis, with North America being the group's most profitable region.

Under Manley, Stellantis' North America region posted a record 16.1% adjusted operating profit margin in the first half of this year.

By 1440 GMT Milan-listed shares in Stellantis were down 0.1%, underperforming a 1.3% rise in Italy's blue-chip index . AutoNation shares were flat.

"It's been my privilege to know Mike first as a competitor, then as a partner and colleague in the creation of Stellantis, but most importantly, always as a friend," said Stellantis CEO Carlos Tavares, who formerly lead PSA.

Stellantis said that Manley will join the board of the Stellantis Foundation, the carmaker's charitable arm.

An investment banker, who has worked with FCA, said Manley's ambition was to become a CEO again.

"I think he realized he had to wait too much time to go back to the top in Stellantis," he said.

Stellantis said its chief operating officers of North America and Latin America would now report directly to the group's CEO Tavares. (https://bit.ly/3kukCRE)

Manley will take charge at Ft. Lauderdale, Florida-based AutoNation effective Nov. 1.

The move solves a succession challenge for AutoNation, which had revenue of $20.4 billion in 2020.

Jackson has been at the helm for over two decades and two previous attempts to replace him in recent years failed.

The move comes as U.S. auto retailers are reporting bumper profits, helped by sales of new and used cars at record prices.

(Reporting by Nick Carey, Giulio Piovaccari and Shreyasee Raj; editing by Shailesh Kuber, Jason Neely and Nick Zieminski)