Ōita (大分郡, Ōita-gun) was a district located in Ōita Prefecture, Japan.
As of 2003, the district had an estimated population of 40,723 and density of 99.35 persons per km2. The total area was 409.90 km2.
As of January 1, 2005 the district had 4 towns.
平成17年10月1日、挾間町と庄内町、そして湯布院町が合併し「由布市」が誕生しました。