FLT can refer to:
- Fairlight (group), a warez release group
- Federación Libre de Trabajadores
- Fédération Luxembourgeoise de Tennis, the governing body for tennis in Luxembourg
- Finger Lakes Trail, system of hiking trails in upstate New York
- First-line treatment or First-line therapy
- Fermat's Last Theorem
- Fermat's little theorem
- In mathematics two theorems named after Fermat are both referred to as FLT; it more commonly means Fermat's Last theorem.
- FLT, IATA airport code for Flat, Alaska
- flt., abbreviation for the wind instrument technique of flutter-tonguing
- FLT1, FMS-related tyrosine kinase 1, a protein
- Football League Trophy in English football
- An abbreviation for forklift truck commonly used in recruitment listings
- Fractional linear transformation, or Möbius transformation
- Free Territory of Trieste
- Front de Libération du Tchad or Liberation Front of Chad
- -3'-fluoro-3'-deoxy-L-thymidine, a PET tracer used for medical imaging
- An acronym (for "Friendship, Love, and Truth") sometimes seen on tombstones, signifying membership in the Oddfellows