Jamal Khashoggi was murdered in Istanbul in 2018. AFP
The man, bearing a passport in the name of Khalid al-Otaibi, was "quickly" able to head for Riyadh, the Saudi embassy in Paris said in a statement, adding that its diplomats had visited him during his detention.
French border police had arrested him at Paris's main airport on Tuesday as he prepared to board a flight to Riyadh.
Police and judicial sources initially told French media that he was the Khalid al-Otaibi wanted under an international arrest warrant for being part of the hit squad that carried out Khashoggi's murder at the Saudi consulate in Istanbul.
"In-depth verifications to determine the identity of this person have enabled us to establish that the warrant was not applicable to him," the chief prosecutor in Paris, Remy Heitz, said in a statement that admitted to the blunder.
"He has been released," it added, dashing the hopes of campaigners and loved ones who thought the detention spelled a major breakthrough in their quest to bring the perpetrators to justice.
"I only would like to say that I will continue to seek justice in any case," Khashoggi's fiancee Hatice Cengiz told AFP when asked for comment.
'Very Common Name'
Turkey has issued an Interpol Red Notice -- which amounts to an international arrest warrant -- for 26 people over the grisly assassination of the former Washington Post contributor, while the US has also announced sanctions on the alleged killers.
The Saudi embassy in Paris issued a statement late on Tuesday saying that the arrested man had "nothing to do with the case in question" and demanded his immediate release.
A security source in Saudi Arabia added that "Khalid al-Otaibi" was a very common name in the kingdom, and that the al-Otaibi the French thought they were holding was actually serving time in prison in Saudi Arabia along with "all the defendants in the case".
Khashoggi's murder sparked international outrage that continues to reverberate.
The executive director of the DAWN pro-democracy group founded by Khashoggi, Sarah Leah Whitson, called the mistaken arrest a "remarkable display of incompetence" by French police, but she stressed what she called the "good news."
Saudi Arabia has always insisted that its legal process, carried out behind closed doors, has been completed and there is no need for any further arrests.
"The Saudi judiciary has issued verdicts against all those who took part in the heinous murder of Jamal Khashoggi, all of them are currently serving their sentences," the Paris embassy said.
In September 2020, a Saudi court overturned five death sentences issued after a trial in Saudi Arabia, sentencing the accused to 20 years in prison instead.
Khashoggi -- a prominent Saudi who lived in self-exile in the US -- entered the Saudi consulate in Istanbul on October 2, 2018, to file paperwork to marry his Turkish fiancee.