A detailed palynological analysis has been undertaken on 200 core and cutting samples selected from seven wells recently drilled in the Murzuq Basin of southwest Libya. The boreholes penetrated Ordovician-Lower Silurian strata belonging to the As Shabiyat, Hawaz, Melez Shugran, Memouniat, Bir Tlakshin and Tanezzuft formations. The majority of the samples proved palyniferous, yielding abundant moderately to well preserved marine palynomophs (acritarchs, chitinozoans, scolecodonts) and non-marine palynomorphs (spores). The palynomorph assemblages enable biostratigraphical age dating and correlation of these strata, in addition to facilitating palaeoenvironmental interpretation. Particularly rich assemblages were recovered from the Melez Shugra Formation and shale intercalations in the Memouniat, Bir Tlakshin and Tanezzuft Formations. However, the As Shabiyat and Hawaz formations yields only rare, poorly preserved, low diversity assemblages characterized by a very low abundance of sphaeromorph acritarchs (Leiosphaerida). A total of 139 species of acritarch, 75 species of chitinozoan and 21 species of spore have been identified. Based on the presence of diagnostic species of acritarch and chitinozoan it is suggested that the Hawaz Formation is Dariwillian in age, the Melez Shugran Formation is late Katian to early Hirnantian in age, the Memouniat and Bir Tlakshin formations are late Hirnatian in age, and the youngest shale of Tanezzuft Formation ranges from Rhuddanian to Telychian in age. Regarding the variation in the proportion of different palynomorphs types, the depositional environment is interpreted as fluviatile to marginal marine in the Ash Shabiyat Formation, marginal marine to marine inner shelf in the Hawaz Formation, and marine inner shelf in the Melez Shugran Formation. Acritarchs are present in shale intercalations in the Memouniat Formation and are very similar to those of the silty shale of the overlying Bir Tlakshine Formation suggesting that the depositional environment is marine inner shelf. The hot shales of the Tanezzuft Formation were deposited in marine environments relating to maximum flooding events during the Rhuddanian. They pass up into marginal marine environments.