But the formal, ornate style of the sumptuous gown by Carolina Herrera reflected French esthetics, from the intricate beaded black bodice, to the train and full skirt in a colour called liberty blue, according to Susan Swimmer, author of "Michelle Obama: First Lady of Fashion and Style."
"From the White House to Versailles it's not that far," said Swimmer, who is also contributing fashion features editor for More magazine. "It's much more keeping in a French esthetic than I've seen her wear before. It's very French in terms of how ornate it is and the use of lace and the velvet sash."
The gown featured a black, hand-sewn beaded embroidery applique scallop-edged top that came to Obama's elbows. The top went over a blue silk faille corset and long skirt with a train that billowed behind the first lady as she walked with President Barack Obama. It was matched with a black velvet belt. The colour also echoed the blue colour that both countries share in their flags.
The White House confirmed it was a Herrera gown and Herrera took credit in a news release saying she made the dress at her New York atelier.
The first lady, however, is known for wearing silhouettes that are more sleek and glamorous. Take, for example, the strapless and sequined custom-made Naeem Khan column gown she wore to the state dinner for India in 2009.
Tuesday evening's dress had a vibe that was more couture and elegant, said Kate Betts, author of "Everyday Icon: Michelle Obama and the Power of Style."
"It's a very stately dress especially for her because she usually wears something much more streamlined," Betts said.
The dress also did something that's a bit of a rarity. It covered Michelle Obama's famously toned arms.
"I don't know that she's ever worn sleeves for a formal occasion," Swimmer said. "Why would she? She's got fabulous arms!"
The first lady had the fashion spotlight to herself during the evening's events. That's because Hollande was without a date after a very public breakup with his longtime girlfriend, Valerie Trierweiler. It meant the American president's wife was the centre of attention, seated next to the tuxedoed French leader.
Michelle Obama is no stranger to Herrera's work. She's worn the designer before, as recently as a September luncheon in New York for the spouses of foreign dignitaries.