PARIS — Fifty years ago, almost to the day, students here began to strike over the rigidity and hierarchy of the French university system, defying the historical deference of young people to their elders; the same day, workers at a major factory near Nantes walked out.

Within days, the strikes spread to other universities and factories, and garbage collectors and office workers joined in. By mid-May, more than 10 million people across France were on strike, and the country had all but come to a standstill.

The protests of 1968 ushered in more than five years of social upheaval, intensifying an antiwar movement in Europe and contributing to the women’s liberation and gay rights movements. And it all started with a call to upend the old order.

“There was an idea that France was a class society and it had to be torn down,” said Éric de Chassey, a professor of contemporary art who curated, with Philippe Artières, “Clash of Images,” an exhibition at the Beaux-Arts de Paris. It showcases posters from those early days of social upheaval, as well as art and documents from subsequent protests for women’s rights and gay rights.