DIA or Dia may refer to:

• Defence Industry Agency, Turkey
• Defense Intelligence Agency, United States foreign military intelligence agency
• Defence Intelligence Agency (India) Indian foreign military intelligence agency
• Defence Intelligence Agency (Nigeria)
• Defense Intelligence Agency (South Korea)
• Department of Internal Affairs, New Zealand public service department
• Department of Indian Affairs, Canadian federal department
• Direzione Investigativa Antimafia, an Italian law-enforcement agency

• Davao International Airport (DVO)
• Denver International Airport (DEN)
• Dubai International Airport (DXB)
• Doha International Airport (DIA)
• Durban International Airport (DUR)
• Washington Dulles International Airport (IAD)

• Design Institute of Australia, Australian design organisation
• Detroit Institute of Arts, American art museum
• Dia Art Foundation, non-profit arts organization

• Design and Industries Association, British charity

• Dubai International Academy, a private school in the United Arab Emirates.

• Dia (film), a 2020 Indian Kannada language film
• DIA (group), a South Korean girl group
• Dia (singer), stage name for Kim Ji-Eun, a South Korean female singer

• Dia (supermarket chain), Spanish multinational supermarket chain

• Detroit International Academy for Young Women
• Development in Action (DiA), a youth-led UK NGO focusing on international development and global citizenship amongst young people
• Sakartvelos Gogona Skautebis Asociacia 'Dia', the Georgian Girl Scout Association

• Diá, Drôme, France
• Dia (Bithynia), an ancient town of Bithynia
• Dia (Coele-Syria), an ancient city of Coele-Syria
• Dia (island), Greek island off the coast of Crete
• Dia, Mali
• Dia (moon), a moon of Jupiter
• Naxos (island), Greek island in the Aegean, named Dia by the ancient Greeks

• Al Día (disambiguation), various newspapers
• El Día (disambiguation), various newspapers
• O Dia, Brazilian newspaper
• Türkiye Diyanet Vakfı İslâm Ansiklopedisi (DİA) or İslâm Ansiklopedisi, Turkish encyclopedia for Islamic studies
• El Nuevo Dia Puerto Rican newspaper, commonly referred to as "El Dia"

• Dea Dia, lit. 'goddess Dia', a Roman goddess
• Dia (mythology), name of multiple figures in Greek mythology
• Dia (name), and persons with the name
• Dia language, a Torricelli language of Papua New Guinea
• Dia (software), a software program for diagram creation
• Diameter, the width of a circle, often abbreviated to "dia."
• Diamond (Shugo Chara!), also known as Dia, a character from the manga series Shugo Chara!
• SS Dia, British cargo ship that sank in the Mediterranean in 1964
• Dow Diamonds (NYSE: DIA), an exchange-traded fund tracking the Dow Jones Industrial Average
• Document Interchange Architecture, an IBM standard for electronic mail, part of IBM Systems Application Architecture
• Data-independent acquisition, an acquisition type in mass spectrometry
• Diisopropylamine, a common organic base and precursor to Lithium Diisopropylamide

• Diaa, a given name
• Diya (disambiguation)