Brendan the Navigator, also known as Saint Brendan, was an Irish monk and explorer who lived during the 5th to 6th century. He is best known for his legendary voyage across the Atlantic Ocean, which is detailed in the medieval text called the Navigatio Sancti Brendani. This journey is often considered one of the earliest accounts of transatlantic exploration. Brendan's expedition is said to have taken him to various mystical islands, including Saint Brendan's Island, which some believe may have been located in the North Atlantic. His story has inspired many, contributing to the lore of early European exploration and the spread of Christianity in Ireland and beyond.