With a celebratory fireworks show still to come, onlookers and well-wishers lined the super-scrubbed streets near the cathedral and roared with joy as the newlyweds looked down from a red velvet-covered palace balcony, and haltingly - but deeply - kissed for the crowd.
The church wedding of Prince Guillaume - the 30-year-old heir to the throne and Luxembourg's grand duke-to-be - and the Belgian countess drew top-drawer guest list. It came a day after a civil ceremony at Luxembourg City Hall.
The bearded groom and his 28-year-old blonde bride were trailed by a procession of well-known royals, including Queen Beatrix of the Netherlands, Princess Victoria and Prince Daniel of Sweden, Prince Naruhito of Japan, and Britain's Prince Edward - Queen Elizabeth's youngest child - and his wife, Sophie.
Stephanie plans to renounce her Belgian citizenship in order to - one day - become Luxembourg's grand duchess. The tiny country wedged between France, Belgium and Germany is an important financial center and continues to prosper despite Europe's economic trouble.
Stephanie wore a lace Elie Saab dress with a 5-meter-long wedding train during the ceremony, which was conducted in a mixture of French, German and Luxembourgish. It began with a minute's silence to honor her late mother, Countess Alix de Lannoy.
The nuptials gave tiny Luxembourg - a founding member of the predecessor of the European Union - a rare moment in the international media spotlight. With a population of just over 500,000, the trilingual duchy punches above its weight: Besides being an important financial center, it's home to the world's largest steel manufacturer and it boasts the second-highest gross domestic product per capita in the world, more than $80,000.
Luxembourg began as a Roman fortress. It has, at one time or another, fallen under the control of Spain, France and Austria. In 1839, it gained its independence from the Netherlands, but lost more than half its territory to Belgium. Germany overran Luxembourg twice in the 20th century despite its protests of neutrality.
The current grand duke, Henri, who is 57, is popular. People can greet him on the street without bowing down before him. His 31-year marriage to Grand Duchess Maria Teresa appears to be very happy.
The newlyweds seem to be happy too: In public appearances, including at the London Olympics, they have appeared besotted with each other.
After watching the ceremony on a big-screen on a public square near the cathedral, royal-gazing fans sensed the joy and historical importance.
"It was a really big moment - a really beautiful moment," said Claudine Als, clutching a glass of Champagne, seemingly awaiting a toast. "It is a historic day for Luxembourg, the country shines throughout the world."