Obama Onsen is an onsen (hot spring resort) in Obama, Unzen, Nagasaki Prefecture, Japan. It is known for having the hottest and most active springs in Japan, with some of them reaching 80-100 °C and producing over 15,000 tons of hot water daily. Its location near the seashore allows one to see the sun setting, which makes it a popular place to visit in the evenings. The poet Saito Mokichi wrote about Obama Onsen in his poem Sunset Plaza (Y?hi no Hiroba), and a monument with the words of the poem was erected near the onsen. The area was formerly part of Hizen Province. The onsen was designated as a National Recreation Onsen in 1962, and was first recorded in a topographic record (Hizen Fudoki) in 713. A fireworks show is held annually in December.