DAK or dak can refer to:
- Dak, a Hindi word for "mail"; also used for a British colonial postal and passenger transport service in India.
- Dak bungalow, travellers' accommodation in India.
- "Dak" was slang in some countries for the C-47 Dakota military transport aircraft.
- DAK, an abbreviation for "Double above knee" in terms to describe an amputee who is legless, in contrast to DBK, quoting amputation below the knees.
- DAK Industries, a US discount electronics retailer
- DAK Simpson, a clothing brand in the UK, which gave rise to an Australian vernacular term for trousers: "daks" (or "dacks").
- Danish Crown AmbA (DAK), a Danish producer of meat products
- Deutsches Afrikakorps, the German Afrika Korps of World War II
- Disney's Animal Kingdom, a theme park at Walt Disney World in Florida
- Double Action "Kellerman", a type of firearm action developed by Sig Sauer
- Paper Mulberry, tree also known as Dak
- "Dak" is slang in some countries for Marijuana