Millions of people around the world waited with baited breath to find out the name of the newborn prince and fifth in line to the British throne.
And after days of fevered speculation, William and Kate plumped for a name used for centuries across the Channel by the French, who have had 18 kings called Louis.
A portrait of the renowned French chemist, Louis Pasteur (1822-1895)
Louis XIV, known as Louis the Great or the Sun King, was a monarch of the House of Bourbon who reigned as King of France from 1643 until his death in 1715
Louis Tomlinson, the singer-songwriter from One Direction, now shares his name with the fifth in line to the throne
Louis Armstrong was a world-renowned musician and singer, perhaps best known for his rendition of What a Wonderful World
The first French king was Louis I, known as ‘Louis the Pious’, who reigned between 778 and 840.
The most famous was Louis XIV, known as the Sun King, whose reign started aged four and lasted 72 years and 110 days – the longest recorded of any monarch of a sovereign country in European history. Queen Elizabeth’s reign is currently in its 66th year.
The last one was Louis XVIII – who reigned for a year until Napoleon took power for a second time in 1815 and ensured the monarchy was destroyed.
Prince Louis of Luxembourg, 31, is the third son of the Grand Duke Henri and Grand Duchess Maria Teresa of Luxembourg.
The name is also shared by Louis Tomlinson, the singer-songwriter from One Direction. The 26-year-old was born in Doncaster before joining the boyband, who went onto worldwide fame after appearing on the X Factor.
He later appeared as a guest judge on the show before launching a number of solo projects. He has a son with now-ex-girlfriend Briana Jungwirth.
Louis Armstrong was a world-renowned musician and singer, perhaps best known for his rendition of What a Wonderful World.
Born and raised in New Orleans in 1901, his instantly recognisable gravelly voice and unparalleled trumpet skills saw him rise to prominence in the jazz scene during the 1920s.
The Duchess of Cambridge meets Louis Tomlinson on stage at the Royal Variety Performance at the London Palladium in London in 2017
Tomlinson,26, was born in Doncaster before joining the boyband, who went onto worldwide fame after appearing on the X Factor
He enjoyed a long career spanning five decades, culminating with his induction into the Rhythm & Blues Hall of Fame in 2017. He died in New York City in 1971.
Fashion-conscious Kate could even have been influenced by one of her favourite luxury fashion houses, Louis Vuitton.
The 164-year-old French label, named after its founder, has become one of the world’s leading retail companies and was valued at £13.7billion in 2017.
The French fashion designer lived from 1821 to 1892. He went from poverty in rural France and trekked into Paris before becoming the apprentice to a box-maker.
He later launched his own brand and was hired as personal box maker and packer to the Empress of France, under Napoleon III. Since his death, a fashion brand bearing his name has become a global brand.
Other famous bearers of the name include French scientist Louis Pasteur (1822-1895) and Métis leader Louis Riel (1844-1885), who led a rebellion against Canada.
Born and raised in New Orleans, Louis Armstrong’s instantly recognisable gravelly voice and unparalleled trumpet skills saw him rise to prominence in the jazz scene during the 1920s
Louis Pasteur was born on December 27, 1822 in Dole, France and died on September 28, 1895, in Saint-Cloud.
A chemist and microbiologist, he was one of the most important founders of medical microbiology.
Among his contributions to science and medicine include the discovery that microorganisms cause fermentation and disease. He thus developed the process of pasteurization and vaccines against anthrax and rabies.
Popular BBC presenter and British journalist Louis Theroux, meanwhile, is known for his probing documentaries. He graduated from Oxford in 1991 and started out as a print journalist before going on to forge a career in television.
Pottermore, author JK Rowling’s publishing company, has pointed out that Louis, Arthur and Charles are all members of the famous Weasley family from the Harry Potter books.
The official Twitter account tweeted: “Louis Arthur Charles, you were named after three iconic Weasleys… #RoyalBabyName”