Before the fifth century

Radiocarbon dating puts the oldest surviving archaeological artifacts from Slovakia – found near Nové Mesto nad Váhom – at 270,000 BC, in the Early Paleolithic era. These ancient tools, made by the Clactonian technique, bear witness to the ancient habitation of Slovakia. Other stone tools from the Middle Paleolithic era (200,000 – 80,000 BC) come from the Prévôt cave near Bojnice and from other nearby sites. The most important discovery from that era is a Neanderthal cranium (c. 200,000 BC), discovered near Gánovce, a village in northern Slovakia.

Archaeologists have found prehistoric Homo sapiens skeletons in the region, as well as numerous objects and vestiges of the Gravettian culture, principally in the river valleys of Nitra, Hron, Ipel, Váh and as far as the city of Žilina, and near the foot of the Vihorlat, Inovec, and Tribec mountains, as well as in the Myjava Mountains. The most well-known finds include the oldest female statue made of mammoth-bone (22 800 BC), the famous Venus of Moravany. The statue was found in the 1940s in Moravany nad Váhom near Pieštany. Numerous necklaces made of shells from Cypraca thermophile gastropods of the Tertiary period have come from the sites of Zákovská, Podkovice, Hubina, and Radošinare. These findings provide the most ancient evidence of commercial exchanges carried out between the Mediterranean and Central Europe.
From around 500 BC, the territory of modern-day Slovakia was settled by Celts, who built powerful oppida on the sites of modern-day Bratislava and Havránok. Biatecs, silver coins with the names of Celtic Kings, represent the first known use of writing in Slovakia. From 2 AD, the expanding Roman Empire established and maintained a series of outposts around and just north of the Danube, the largest of which were known as Carnuntum (whose remains are on the main road halfway between Vienna and Bratislava) and Brigetio (present-day Szöny at the Slovak-Hungarian border). Near the northernmost line of the Roman hinterlands, the Limes Romanus, there existed the winter camp of Laugaricio (modern-day Trencín) where the Auxiliary of Legion II fought and prevailed in a decisive battle over the Germanic Quadi tribe in 179 AD during the Marcomannic Wars. The Kingdom of Vannius, a barbarian kingdom founded by the Germanic Suebian tribes of Quadi and Marcomanni, as well as several small Germanic and Celtic tribes, including the Osi and Cotini, existed in Western and Central Slovakia from 8–6 BC to 179 AD.