A Syrian pro-regime site called on residents of the capital Damascus to demonstrate their support for Assad by joining a convoy of cars in the Mazzeh district to honour him.
Assad, a British-trained ophthalmologist who has three children, succeeded his father Hafez, who died in 2000.
He came to the position of heir unexpectedly, after his brother Bassel was killed in a car accident.
Once considered a potential reformer, who discussed the need for political and economic openness after he took office, Assad has responded with an iron fist to an uprising that began in March 2011.
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He marks his birthday as the threat of imminent US-led strikes against his regime appears to have waned.
The strikes, which were intended to punish the regime for allegedly using chemical weapons on August 21, appear to be on hold as a Russian proposal that Syria hand over its chemical weapons is discussed.
Inside Syria, Assad is believed to have a firm grip on his regime, more than two years after the uprising began.
"He listens to his advisors, but he takes the decision by himself," adds an expert based in Beirut.
Assad's confidantes include his brother Maher al-Assad, a colonel who heads the division in charge of Damascus, as well as his wife Asma.
His inner circle also includes his uncle and cousin Mohammed and Rami Makhlouf, two businessmen, and Hafez Makhlouf, his security chief in Damascus.
But he also counts Druze among his closest advisors, including minister of presidential affairs Mansour Azzam and Louna al-Shibi, a former journalist.
Others close to him include Alawite Hussam Sukkar, a general and his presidential security advisor, and two senior Sunni intelligence officials -- Gen Ali Mamluk, who heads national security, and Gen Rustom Ghazaleh, head of political security.