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)