The United Nations refugee agency said Lebanon is now hosting more than 1 million Syrian refugees who have fled their country's three-year-old crisis.
The UNHCR said the "devastating milestone" was reached Thursday, and that Lebanon is struggling to keep up with the influx. Lebanon's own population is about 6 million people.
U.N. High Commissioner for Refugees Antonio Guterres called the impact "staggering" and said Lebanon needs more help to provide services.
The U.N. has asked for more than $4 billion to aid Syrian refugees in the region this year, with nearly half that total for Lebanon alone. Donations so far have reached about 13 percent of that total.
The World Bank said the Syrian crisis has hurt Lebanon's economy, with an estimated $2.5 billion in lost economic activity last year.
Refugees have fled Syria in increasing numbers as fighting there has continued and international efforts to broker peace have failed to produce any real progress.
In April 2012, the U.N. had registered about 30,000 Syrian refugees. Last April, that number was about 1 million. Today, there are 2.6 million Syrian refugees in addition to 6.5 million people displaced within the country.
Turkey hosts the second highest number of refugees with 668,000, followed by Jordan with 589,000, Iraq with 220,00 and Egypt with 136,000.
The U.N. has stopped issuing updated death tolls in Syria, but has reported that well over 100,000 people have died in the fighting. The Britain-based Syrian Observatory for Human Rights said this week its own count now exceeds 150,000 dead.
Rescuers help an injured civilian at a site hit by what activists said were barrel bombs dropped by forces loyal to Syria's President Bashar al-Assad in Aleppo's al-Sakhour district, April 2, 2014.
A damaged building is pictured in Masaken Hanano, Aleppo, April 2, 2014.
Free Syrian Army fighters prepare a rocket propelled grenade launcher before heading to the front line in Khan Sheikhoun in northern Idlib province, April 2, 2014.
Fighters from Islamic State in Iraq and the Levant burn confiscated cigarettes in the city of Raqqa, April 2, 2014.
Fighters from the Free Syrian Army's Al Rahman legion help a wounded comrade in Mleha suburb of Damascus, April 2, 2014.
A rebel fighter gestures as he runs across a street in Mleha suburb of Damascus, April 2, 2014.