Lai or LAI may refer to:

• Austrian Latin America Institute (Österreichisches Lateinamerika-Institut)
• Latin American Idol, TV series
• La Trobe Institute, Melbourne, Australia
• Leaf area index, leaf area of a crop or vegetation per unit ground area
• League against Imperialism, transnational anti-imperialist organization in the interwar period
• Liga Atlética Interuniversitaria de Puerto Rico
• Location Area Identity

• Laindon railway station, Essex, England (National Rail station code LAI)
• Lannion – Côte de Granit Airport, Brittany, France (IATA airport code LAI)

• Lai (state) (萊), 6th-century BC state in present-day Shandong, China
• Bolyu language, also known as Lai
• Laï, city in Chad
• Lai, Iran (disambiguation), places in Iran
• Lai, village in Lum Choar, Cambodia
• Lai, Romansch name for Lenzerheide, a village in Switzerland

• Lai (surname) 賴, 黎丶Chinese surname
• Lí (surname 黎), Lai in Cantonese
• Francis Lai (1932–2018), French composer
• Valentino Lai (born 1984), Swedish football player

• Long-acting injectable, a type of drug form

• Battle of Lai, during World War I
• Lai people, ethnic group of Mizoram, North East India
• Lai languages
• Lai (poetic form) or Lay, song form in medieval France

• Lais (disambiguation)