A bipolar junction transistor is a type of transistor that uses both electrons and holes as charge carriers.

BJT may also refer to:

• Balanta language (ISO 639: bjt), an Atlantic-Congo language of West Africa
• Beijing Time, another name for China Standard Time
• Bentota River Airport (IATA: BJT), Sri Lanka
• Bhumjaithai Party, a Thai political party
• Business Japanese Proficiency Test, a test of practical communicative ability in Japanese