Ireland was not "discovered" in the colonial sense. Humans arrived during the Mesolithic period (~8000 BCE), crossing from Britain via land bridges or coastal routes. The Neolithic (~4000 BCE) brought agriculture, megaliths (Newgrange), and permanent settlements. By the time written records begin (early Christian period, 5th century CE), Ireland had a complex Gaelic society with kingdoms, law (Brehon), and literacy (Ogham). The concept of "discovery" applies to lands unknown to a civilization—not to places already inhabited for millennia.