Originally known as "Muang Narang," Prachuap Khiri Khan was abandoned following the second fall of Ayutthaya to Burmese forces. In the early Rattanakosin period, King Rama II established a new settlement at Khlong Bang Nang Rom and later moved the administrative center to Kui Buri. Under King Rama IV, the area was officially renamed Prachuap Khiri Khan, though the main administrative offices remained in Kui Buri.

During the reign of King Rama V, the neighboring cities of Pran Buri, Prachuap, and Kamnoet Nopphakun were consolidated under the name "Pran Buri," with administrative headquarters at Ao Ko Lak. The original Pran Buri was then re-designated as a district. However, local residents continued to refer to the new administrative center by the name Pran, which led to confusion with the nearby Pran Buri. Recognizing this, King Rama VI ordered the name change to Prachuap Khiri Khan, a name that the province has retained to this day.