The listing of the Qhapaq Nan roads will boost efforts to preserve and promote the network -- an engineering marvel comparable to the vast road system of the Roman Empire.
Delegates at UNESCO's World Heritage Committee voted to grant the status at a gathering in Doha, where they are considering some 40 cultural and natural wonders for inclusion on the UN list.
Covering some 30,000 kilometres and constructed by the Incas over centuries, the system has long connected the peoples of Argentina, Bolivia, Chile, Colombia, Ecuador and Peru.
Inclusion on the list has significant economic implications as a World Heritage Site is eligible for financial assistance toward preservation and the status is also a powerful draw for tourists.
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"This is a recognition of one of the most important sites in the world," Luis Lumbreras Flores, who is responsible for the Qhapaq Nan project at Peru's culture ministry, told AFP.
The road system, which reached its height in the 15th century, linked the Incan capital Cusco in present-day Peru with the vast reaches of the empire.
"It demonstrates mastery in engineering technology," UNESCO said, calling it "an exceptional and unique testimony to the Inca civilisation".
The system, which began forming as trails thousands of years ago, linked some 40,000 people of the Incan Empire, carrying traders, travellers, messengers and armies.
The road system was eventually used by the mounted Spanish conquistadors in their exploration and conquest of the continent after their arrival in 1526.