Altai or Altay may refer to:

• Altai Mountains, in Central and East Asia, a region shared by China, Mongolia, Kazakhstan and Russia

• Altay Prefecture (阿勒泰地区), Xinjiang Uyghur Autonomous Region, China
• Altay City (阿勒泰市), also spelled "Aletai", a city of Altay Prefecture

• Altai Town, a town in Kazakhstan, until 2019 known as Zyryan or Zyryanovsk

• Altai City
• Altai, Govi-Altai, a sum (district)
• Altai, Bayan-Ölgii, a sum
• Altai, Khovd, a sum

• Altai Krai, a federal subject of Russia
  • Altay, Altay Krai
• Altai Republic, a federal subject of Russia

• Altay (name), a list of people with the given name or surname
• Altai people, an ethnic group
  • Altai languages, the languages spoken by these people

• Altai, a historical novel by Wu Ming
• Rupes Altai, a feature of the geography of the Moon
• Altay sheep, a sheep breed
• Altay S.K., a football club from İzmir, Turkey
• Altay S.K. (women's football), women's football team from İzmir, Turkey
• Altay (tank), a Turkish main battle tank
• Altay-class oiler, a Soviet Navy ship class
• Altai gas pipeline, a proposed natural gas pipeline between Russia and China
• Altai (mobile telephone system), a Soviet pre-cellular radiotelephone service
• Aletai meteorite, a very large meteorite which consists of several fragments found in the Altay Prefecture

• Altaysky (disambiguation)
• Alt-A, a type of U.S. mortgage
• Computer Associates International, Inc. v. Altai, Inc., a US legal case