Port Arthur may refer to:

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

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

• Port Arthur, China, now called Lüshunkou District, in the city of Dalian
  • 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

• VIII District, Turku, a district in Turku

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

• Port Arthur (film), a 1936 drama film directed by Nicolas Farkas