The reinforcement of links with Paris comes as Riyadh worries over an Iran nuclear deal and fights Iran-backed rebels in neighbouring Yemen.
Fabius, on his Saturday-Sunday visit, was welcomed more as a head of state than a minister, meeting the entire leadership of the kingdom.
"I'm not surprised, given the momentum that the relationship has taken in the last few years," said Asaad al-Shamlan, a political science professor at Riyadh's Institute of Diplomatic Studies.
Fabius met King Salman, Crown Prince Moqren, Deputy Crown Prince and Interior Minister Mohammed bin Nayef, along with the king's son Defence Minister Mohammed bin Salman, who leads the kingdom's war against Shiite Huthi rebels in Yemen.
The French minister also held talks with Riyadh's veteran Foreign Minister Prince Saud al-Faisal.
Saud, who has seen ties with France grow in recent years, stressed at a joint press conference "the friendship and trust" between the two countries.
Fabius sought to reassure his hosts over an April 2 framework agreement between major powers and Iran to curb its nuclear ambitions.
The West and Sunni Gulf states fear Tehran wants to build an atomic bomb but Shiite-dominated Iran -- Saudi Arabia's regional rival -- insists its nuclear programme is peaceful.
In exchange for limits on Iran's nuclear capabilities, the accord would lift international sanctions.
A final deal is to be reached by June 30 following further talks between Tehran and six major powers including France.
"There is panic among the Saudis because they think that Iran will use the newly-available finances that a lifting of sanctions will bring (if a final accord is reached) to extend its influence in the region," said Joost Hiltermann of the International Crisis Group of analysts in Brussels.
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Riyadh and Tehran are already divided over Syria, where Saudi Arabia backs Sunni-led rebels while Iran supports President Bashar al-Assad's regime.
Tensions between Iran and Saudi Arabia have risen further since March 26 when a Saudi-led coalition began air strikes against Yemen's Shiite Huthis, who Riyadh says are supported by Tehran.
Iran has rejected accusations of arming the rebels and its supreme leader Ayatollah Ali Khamenei has condemned the air strikes as "criminal acts".
Fabius did not announce any military assistance for the Saudi-led coalition but said he came "to demonstrate our support, especially political".
Saudi Arabia fears that if too much of Iran's nuclear programme is left intact, Tehran will still have the ability to obtain an atomic bomb, and there are concerns that Riyadh could seek its own nuclear capability.
Analysts say Paris has taken a harder stance than Washington in the nuclear talks, to the satisfaction of Gulf nations.
And Riyadh and its partners in the Gulf accuse Washington of having abandoned Egypt's president Hosni Mubarak, their ally overthrown in a 2011 uprising, while failing to act against Assad, said David Butter of London's Chatham House think-tank.
He said there are "clearly a lot of tensions in the relationship" between Riyadh and the United States, even if Washington remains the kingdom's primary military supplier and the two sides continue to work together.
Shamlan, of the Institute of Diplomatic Studies, said that despite some strains the overall relationship between Saudi Arabia and the US is "very good".
"The value of the relationship is very much appreciated by both sides," he said, and a strengthening of ties with France or other countries does not come at the expense of links with the US.
"There's no contradiction between having a close relationship with the United States and having a close relationship with France or Britain and certainly with China," he said.
The kingdom's ties with Britain have been "growing tremendously" over the past 15 years on the back of defence deals, Shamlan added.