The Celts, a collection of Indo-European tribes, shared common linguistic and cultural traditions. They controlled extensive territories across Europe from 1200 BCE to 400 CE, spanning from Ireland and Scotland to Anatolia and from the Netherlands to Spain and Italy. Greek and Roman observers frequently wrote about the Celts in negative terms but also expressed their admiration for them. The main Celtic communities consisted of the Gauls, Celtiberians and Gallaeci from Iberia, the Britons and Picts from Britain and Ireland, and the Galatians from Anatolia. Archaeologists have obtained most of their information from two primary archaeological sites, Hallstatt, Germany (800–450 BCE) and La Tène, Switzerland (450 BCE–50 CE), named after where distinctive artifacts were discovered. 

The social organization of the Celts followed a tribal system with multiple layers of hierarchy. The ruler of each nation held the position of king or queen. Historical records remember Boadicea from the Iceni and Vercingetorix from the Gauls as leaders who fought against Roman territorial expansion. The tribal system organized its population into three distinct social classes: chieftains, warriors, and druids. The druids performed priestly duties and served as judges and scholars, functioning as spiritual leaders, conflict mediators, and protectors of cultural knowledge. The warriors, notorious for fighting naked, gained fame through their aggressive combat abilities, together with distinctive equipment and frightening battlefield methods. They fought using longswords, spears, and shields that often displayed complex metalwork designs. The Celtic pantheon contained hundreds of deities, including Lugh, Morrigan, and Brigid, who were associated with natural events, warfare, and fertility. Women in Celtic society enjoyed more influence than female members of other pre-Christian European communities and could own property, practice medicine, and initiate divorces. The Celts developed complex metalwork, along with decorative art that later included Celtic crosses and illuminated manuscripts such as the Book of Kells.

Barley, wheat, cattle, and sheep formed the basis of their agricultural production. Inadequate winter vitamin intake sometimes caused them to develop scurvy. Medical evidence from archaeological sites shows that they may have also suffered from iron-deficiency anemia and parasitic diseases. Traumatic injuries were widespread among Celtic warriors because of tribal conflicts, leading to sword wounds and bone fractures, and demonstrating their skilled approach to bone setting and immobilization. The combination of herbal medicine and spiritual rituals formed part of their healing practices, which drew from their extensive knowledge of medicinal plants such as foxglove, juniper berries, wild garlic infusions, and seaweed. The Celtic healers and druids also used mistletoe together with sacred medicinal plants such as yarrow and willow bark. Willow bark, containing salicin, a chemical precursor to contemporary aspirin treatment, probably served for both relieving pain and  reducing fever. The medical property of clotting in yarrow led people to use it to control bleeding when treating wounds. During healing ceremonies, practitioners performed sacred incantations while making divine offerings and using magical charms. The discovery of inscribed tablets reveals that sacred spring water was used as a form of treatment. Burial sites uncovered during archaeological excavations have shown evidence of trepanning or drilling skulls.

Archaeological research has uncovered many cases of advanced medical practices. The examination of a wounded Iron Age Celtic warrior revealed that he survived severe pelvic trauma through sophisticated medical treatment which successfully managed his injury. This demonstrates an unexpected level of surgical expertise and wound care knowledge that contradicts popular beliefs about ancient medical abilities. Limited documentation exists, but these physical discoveries illustrate the extent of their medical expertise. Traditional wound treatment included using natural substances such as honey, due to their antibacterial properties and healing capabilities. People considered water to hold both sacred and healing attributes. Water bodies, including lakes, rivers, and streams, were believed to possess healing properties, which led people to bathe in or drink from them for medical recovery. Some people performed rituals by walking around wells as they offered presents to the water deities who they believed were responsible for their illnesses.

The Roman conquest of Gaul and Britain integrated Celtic medical traditions with Greco-Roman medical practices. Roman medical experts documented Celtic use of herbs along with their sacred practices, and sometimes recognized their surprising effectiveness. Their early contributions to medicine remain significant, particularly the use of willow bark and several surgical procedures that also proved effective in later historical periods and cultural settings.