The four men, largely of north African descent who grew up in working-class French suburbs, were apprehended in the U.S. campaign to topple Afghanistan's Taliban regime in 2001 and 2002.
Supporters hailed the return — the first by any French nationals from the American base — and President Jacques Chirac said the handover was the fruit of longtime talks between Paris and Washington.
The four arrived by plane at a military base in Normandy, then were taken by bus to Paris to appear before counterintelligence agents and anti-terrorism judge Jean-Louis Bruguiere, officials said.
Seven French nationals in total were detained at Guantanamo, and the handover of at least some had been expected after the French Foreign Ministry announced U.S.-French talks on the matter last month.
"It's the result of long efforts," Chirac told reporters during a visit to Madagascar. "We will naturally continue the discussions with American authorities to obtain the handover of the two or three other detainees."
While historic allies, France and the United States have been at odds for more than a year over issues such as the best way to fight against terrorism, Turkey's bid to join the European Union, the Middle East and the U.S.-led Iraq war and its aftermath.
The four suspects, who remained in custody, were to be placed under investigation for criminal association with a terrorist enterprise, officials said. They did not speak with reporters.
After months of international criticism for holding hundreds of suspects at Guantanamo Bay without charge, the United States has been gradually releasing some detainees from its naval base in Cuba.
Last month, the U.S. military said 134 suspects had been freed, including Afghan, Swedish, Spanish, Danish and British nationals. Once home, some have been released without charge.
The French nationals handed over were Mourad Benchellali, Imad Kanouni, Nizar Sassi and Brahim Yadel, judicial officials said. They were remanded to French custody over the weekend, they said.
Under French anti-terror laws, they can be held for questioning for up to 96 hours.
Three other French detainees remain at Guantanamo — Ridouane Khalid, Khaled Ben Mustafa and Mustaq Ali Patel, who has both French and Indian citizenship, the officials said.
Defense lawyer Jacques Debray, speaking to The Associated Press, expressed "great satisfaction" that his two clients were among the four returning to France. He represents Benchellali, 24 and Sassi, 22, who hail from a working class suburb of the southeastern city of Lyon.
William Bourdon, another lawyer for those two men, said, "France made it known to the Americans ... that the last word would rest with the investigating magistrate" once they returned.
"Consequently, if there were very strong pressures (by the U.S. government) that they be locked up, the weakness or emptiness of the charges supposedly collected on them should lead to a very fast release after they are taken into custody," he said.
Some of the detainees have been sought by French investigators.
Yadel is wanted in connection with an investigation into a training camp by Islamic militants set up in the late 1990s in the Fontainebleau forest south of Paris. Some of those at the camps are believed to have traveled to Afghanistan and the breakaway Russian republic of Chechnya.
Benchellali is the son of Chellali Benchellali, an imam from the Lyon suburb of Venissieux who was arrested in connection with a suspected terrorist network that authorities say was planning attacks on Russian interests in France. The imam remains in custody.
"The important thing to know now is the mental, physical and psychological health of these youths, and what the conditions of their detention were for 30 months," said Venissieux mayor Andre Gerin.
Gerin said the French Foreign Ministry had been actively negotiating toward the handover of the suspects since November.
The Guantanamo Bay camp holds about 600 inmates. Many are believed to be foot soldiers from the al Qaeda terror network and Afghanistan's deposed Taliban regime, while some may be victims of circumstance.
The International Committee of the Red Cross and other human rights groups have expressed reservations about the U.S. military's practice of holding the prisoners at Guantanamo without charges.
The Pentagon has held most of the detainees at Guantanamo Bay without charge for more than two years on grounds that they are "enemy combatants" with no right to contest their detention in U.S. courts.
The Pentagon set up "Combatant Status Review Tribunals" for Guantanamo detainees after the U.S. Supreme Court ruled June 28 that they have a right to bring challenges before U.S. civilian courts.
By Pierre-Antoine Souchard