In Roman times, the region was the westernmost limit of the Roman Empire. Near modern-day Obidos was a town called Beleza Moreira, about which little is known due to its recent discovery. After the fall of the Roman Empire, the Moors took over most of the Iberian Peninsula and ruled the Obidos area until 1148. In that year, Afonso Henriques captured and claimed the town for Portugal. In 1195, the town received its first charter under the second king of Portugal, Sancho I.

Under Portuguese rule and thanks to its location along the Atlantic Ocean, Obidos flourished into a major trading port. It enjoyed the favor of one 13th-century queen, Dona Isabel, to whom Obidos was first given as a wedding present. Unfortunately, by the 16th century, large deposits of silt at the river delta dammed up the harbor area and destroyed the port. However, the city remained a favorite among the royal family of Portugal, and every Portuguese queen after Dona Isabel, up until the 1800s, was given Obidos as a wedding present. Though monarchs no longer rule the country, Obidos continues to be a popular destination during the summer, when tourists jam the streets to explore the city’s medieval charm.