Eliot Spitzer and his young love, Lis Smith, were all smiles after their romantic trip to the City of Light.

The pair was seen Sunday in the first row of first class on an American Airlines jet from Paris to JFK.

“They were moonily grinning at each other and laughing,” said a spy.

It seems Spitzer had reason to celebrate: Sources tell Page Six he just sold off 144 rental units at the Corinthian — the East 38th Street building built by his father in the 1980s — to Gaia Real Estate for $147 million.

Bob Knakal of Massey Knakal marketed the apartments, and we’re told proceeds will go to various Spitzer family interests.

The apartments went up for sale in March, and reports said the deal indicated Spitzer is taking a larger role in his family’s business.

Eliot Spitzer and Lis SmithGC Images

Gaia plans to “renovate, rebrand and sell the units,” the company says.

Spitzer and Smith were spotted on their romantic Paris getaway at the four-star Pavillon de la Reine hotel, where rooms start at more than $500 a night.

Spitzer and the political spokeswoman are both coming off separate, unsuccessful campaigns.