Ulassai () is a comune (municipality) in the Province of Ogliastra in the Italian region Sardinia, located about northeast of Cagliari and about southwest of Tortolì.
Ulassai borders the following municipalities: Esterzili, Gairo, Jerzu, Osini, Perdasdefogu, Seui, Tertenia, Ussassai, Villaputzu.
Ulassai is located in the heart of the Barbagia sub-region of Ogliastra. At 775 meters above sea level, it is the highest town in Ogliastra. Its municipal territory extends for 122 kmò, from the town to the border with the Barbagia di Seùlo and to the south in a small strip with the Province of Cagliari.
The historic center appears nestled between the large complex of the Ulassai Heel to the north and the imposing Mount Tisiddu to the south. On the slopes of the Ulassai Heel lies a complex system of caves, the most famous of which, the Su Marmuri Cave, with its 1,000 meters of length and its internal concretions, is the main tourist destination in the entire Pardu Valley. During periods of heavy rainfall, the impressive Lecorci Waterfalls flow from a lower slope of these caves.
Several Nuragic settlements still exist in the vast municipal area, some destroyed, others still in good condition, such as the nuraghes of S'Ulimu, Seddurrulu, and the giants' tombs of Bau 'e Tuvulu. The area also includes a now-destroyed Nuragic settlement called "Lessei," which was still inhabited until 1350.
The history of Ulassai, despite all the various dominations, has been that of a simple shepherd's life. Until the end of the nineteenth century, the town was not connected by any road to the outside of the Ogliastra area. Only in 1893 were connections to Cagliari achieved through the railway line.
The three schools in the municipality (preschool, primary school, and lower secondary school) are branches of the Jerzu Comprehensive Institute.
The second edition of the Ulassai Contemporary Art Biennale, dedicated to Maria Lai and titled The Meaning of the Work, will be held from late March to early June 2026.
The following important artistic performances have been held in Ulassai in the past: