They highlighted her breakthrough as the first woman candidate for the top job in France and welcomed her "modern" and "dynamic" approach to politics, seen as a welcome, if overtly populist, break with the past.
"A new page in French history has been opened," said the leader of the Party of European Socialists (PES), which brings together socialist and social-democratic parties from across the continent.
"In choosing a resolute and visionary woman, the members of the Parti Socialiste have chosen for France a candidate for the future and have given themselves every chance of beating the right in 2007," PES leader Poul Nyrup Rasmussen said. "Segolene ... will enable France to regain its natural place as a great progressive nation in Europe and the world."
Royal, a telegenic career politician who has built an image as a party outsider infused with fresh ideas, won 60.6 percent of the vote in the Socialist primary on Thursday, trouncing two older male rivals who have already served in government.
A much-needed new dimension
"This is very exciting... It introduces a new dimension in French politics, which is much needed," Norwegian Foreign Minister Jonas Gahr Stoere told AFP.
Kurt Beck, leader of the German Social Democrats, described Royal as "committed and courageous" and predicted her "dynamism" would help her party to election victory.
Several major papers in Europe concurred.
"The day makes history for two reasons," Charles Bremner of Britain's Times newspaper wrote in his weblog. "For the first time, a woman has become a front-line candidate for the French presidency, a monarchical, patriarchal, institution that was tailor-made for Charles de Gaulle in the late 1950s. French presidents are supposed to be elderly men of destiny, good at grandeur, not a youngish woman with television charisma but no clear vision."
"The other novelty is the way that Royal, 53, has emerged as a relative outsider and hijacked the country's most tradition-bound party," the weblog continued.
Modern France wants to turn the page
Italy's Corriere della Serra agreed. "There is another France, which wants to turn the page, which wants to be more modern and European and less attached to a social and state model that multiplies injustices, rather than favoring equality."
La Stampa pointed out that Royal had appealed in particular to young French Socialists. "The Internet generation ... have got rid of 'the elephants', the faded nobility. It's a revolution."
Yet several papers also stressed that Royal's appeal appeared to be based more on image than on substance, and there was little agreement as to what she really stood for.
"Royal differentiates herself from her party colleagues with her radical -- and not at all left-wing -- views," stated Russian Internet newspaper Gazeta.ru.
Not so, said the Times: "Her campaign has resembled (Britain's) New Labor only in its emphasis on moral values, deft use of the media and her ability to connect with the public. On the economy and welfare state she remains firmly in the tradition of French orthodox socialism."
"She's not a classic left-winger. She's seen as realistic. She reminds one of her (expected right-wing) rival Nicolas Sarkozy for her ability to play in her adversaries' court if need be," observed Kommersant in Moscow.
A new phase in French polutics
"Today is the start of a new phase in politics... Nicolas Sarkozy should make haste to show his hand," Italy's Repubblica advised the French interior minister, who is being held back by infighting in his party with outgoing president Jacques Chirac and his supporters.
In the United States, the New York Times said that "in poll after poll, her telegenic smile and elegant profile have appealed to a French public yearning for a new style of leadership," but stressed Royal's "inexperience in foreign policy issues."
The Washington Post said, "She capitalized on her image as a fresh-faced cyber-candidate running an insurgent's campaign to shake up the stodgy male-dominated world of French politics."