Port Arthur may refer to:

• Port Arthur naval base in Manchuria, now called Lüshunkou
  • Port Arthur massacre (China) in the Sino-Japanese War in 1894
  • Battle of Port Arthur, a sea battle in the Russo-Japanese War in 1904
  • Siege of Port Arthur a land battle in 1904

Australia

• Port Arthur, Tasmania (Australia), the site of a historic convict settlement
  • Port Arthur massacre (Australia), which occurred in Port Arthur, Tasmania in 1996

United States

• Port Arthur, Texas, a city in the United States
• Port Arthur, Wisconsin, an unincorporated community

Canada

• Port Arthur, Ontario (Canada), a former city, now a part of Thunder Bay
  • Port Arthur (electoral district) (Canada),

Finland

• VIII District, Turku (Finland), aka Port Arthur, a district in Turku

Other

• Port Arthur, BattleTech Universe's fictional planet