They were then headed to the presidential palace for a mini-summit hastily organised to address tensions over reports of an impending indictment against members of the Shiite militant group Hezbollah for Rafiq Hariri's murder.
It is the first visit to the country by Assad since Hariri's assassination soured bilateral ties and forced the pullout of Syrian troops from Lebanon after a 29-year deployment.
Damascus has consistently denied accusations that it had a hand in the killing.
Relations between the two countries have been on the mend since 2008, when diplomatic ties were established for the first time. Prime Minister Hariri has also made four trips to Syria in the past eight months.
Saudi Arabia, a staunch supporter of the Hariri family, has played a key role in the rapprochement between the Arab neighbours.
Saudi and Syrian flags were being flown throughout the Lebanese capital on Friday for the unprecedented joint visit, along with huge portraits of the king together with a welcome message.
Security was also tight, with additional army and police deployed.
The visit by the Saudi and Syrian leaders is scheduled to last only three hours and includes a lunch to be attended by some 250 officials, among them members of the unity government which includes two Hezbollah ministers.
"The whole visit is about containing the situation for the immediate future," said Sahar Atrache, a Beirut-based analyst with the International Crisis Group think-tank.
"They are here to exert influence on their internal allies ... to prevent a real escalation."
The Arabic-language newspaper An-Nahar, which is close to Hariri's Saudi- and Western-backed governing coalition, called the summit "historic."
"This joint visit is historic and decisive because of its timing and the consequences it can have on a mounting crisis in Lebanon related to the tribunal," it said.
Fears of renewed conflict rose last week after Hezbollah leader Hassan Nasrallah revealed that he knew the UN tribunal probing Hariri's murder was poised to indict members of his party, which is backed by Syria and Iran.
He made it clear that he would not accept such a scenario, accusing the tribunal of being politicised and part of an Israeli plot.
"The Arab leaders' visit to Lebanon is an opportunity to show Arab unity in the face of this plot which aims to destabilise Lebanon and sow sedition," Hezbollah deputy Hassan Fadlallah told AFP.
"This would not be in the interest of the Lebanese or their Arab brothers."
Analysts say that in addition to threatening civil peace, an indictment of Hezbollah members would deal a blow to the party's reputation and destabilise Hariri's unity government.
The Saudi monarch is expected to press Assad to use his influence over Hezbollah to avoid a political stalemate or a sectarian conflict similar to the one which brought Lebanon close to a new civil war in 2008.
Assad last visited Lebanon in 2002, and King Abdullah is the first Saudi monarch to visit the country since 1957.
Also coming to Beirut later on Friday is the emir of Qatar, Sheikh Hamad bin Khalifa al-Thani. The emir, who is staying until Sunday, is to meet separately with Lebanese leaders and due to visit the south of the country.
MOSCOW (AFP) - Eighteen people died in forest fires in Russia's worst heatwave in decades, officials said Friday, as Prime Minister Vladimir Putin visited one of the worst hit areas to reassure local residents. More »
- 5 mins ago
WASHINGTON (AFP) - Israel is skeptical that a new round of sanctions targeting Iran's nuclear program will be effective, but there is "still time" for them to work, Israeli Defense Minister Ehud Barak said Friday. More »
- 1 hour 5 mins ago
BEIRUT (AFP) - Syrian President Bashar al-Assad arrived in Lebanon on Friday for the first time since the 2005 murder of ex-premier Rafiq Hariri in a joint mission with Saudi King Abdullah to defuse a tense political situation. More »
- 1 hour 25 mins ago
BEIRUT (AFP) - Syrian President Bashar al-Assad and Saudi King Abdullah arrived in Beirut on Friday in an unprecedented joint mission to defuse political tensions in Lebanon. More »
- 2 hours 23 mins ago
BEIRUT (AFP) - Syrian President Bashar al-Assad on Friday arrives in Lebanon for the first time since the murder of ex-premier Rafiq Hariri, in a joint mission with Saudi King Abdullah to defuse a tense political situation. More »
- 2 hours 47 mins ago
MOSCOW (AFP) - Eight people died in forest fires in Russia's worst heatwave in decades, officials said Friday, as Prime Minister Vladimir Putin visited one of the worst hit areas to reassure angry residents. More »
- 3 hours 7 mins ago
AMMAN (AFP) - Iraqi Minister of Science and Technology Raed Fahmi was injured on Friday in a road accident in Jordan which killed six people including two British women, police said. More »
- 5 hours 31 mins ago
JERUSALEM (AFP) - A rocket fired by militants in the Gaza Strip slammed into the southern Israeli city of Ashkelon on Friday, causing minor damage but no casualties, a military spokeswoman said. More »
- 6 hours 51 mins ago
BEIRUT (AFP) - Lebanon on Friday hosts a rare summit of regional leaders aimed at defusing tensions over reports of an impending indictment against Hezbollah members for the murder of ex-premier Rafiq Hariri. More »
- Yesterday, 08:40 pm
CAIRO (AFP) - Arab officials agreed in principle on Thursday to the holding of direct Middle East peace negotiations and left it up to Palestinian president Mahmud Abbas to decide when to start talks with Israel. More »
- Israel's Barak, UN chief to discuss Gaza, settlementsAFP -Yesterday, 06:45 pm
- Saudi king in Syria ahead of joint Lebanon missionAFP -Yesterday, 06:30 pm
- 16 dead, 14 wounded in Baghdad attacksAFP -Yesterday, 06:02 pm
- Kites fill skies over Gaza as children reach for recordAFP -Yesterday, 05:47 pm
- Hijacking of plane from Caucasus foiled in Moscow: reportsAFP -Yesterday, 05:32 pm
- Russia 'foils hijacking of plane from Caucasus'AFP -Yesterday, 04:59 pm
- Baghdad attacks kills 16AFP -Yesterday, 04:30 pm
- Israel ready to start direct talks within days: NetanyahuAFP -Yesterday, 04:02 pm
- Arab appeals jailing for consensual sex with JewAFP -Yesterday, 03:37 pm
- Russian president signs law to expand ex-KGB powersAFP -Yesterday, 03:20 pm