BTB may refer to:
In biology:
* Blood–testis barrier in testicular anatomy
* Blood–thymus barrier
* bTB, bovine tuberculosis or ''Mycobacterium bovis'', a disease in cattle
* Breakthrough bleeding, of the menstrual period
* Bromothymol blue, a chemical indicator for weak acids and bases
* BTB/POZ domain, a protein domain
In other uses:
*Belgian Union of Transport Workers, a trade union in Belgium
*Branch target buffer, a computer processor element
*Bétou Airport, in the Republic of the Congo (IATA airport code: BTB)
*Basil Temple Blackwood (1870–1917), British book illustrator (credited as B.T.B.)
*''Bob the Builder'', British children's television series
*Board-to-board connector (BTB)
{{disambiguation