BLK may refer to:
- BLK (gene), gene in humans
- BLK (magazine), American magazine
- blk. (water), a brand of beverage containing fulvic acid and appearing black in color.
- Blackpool International Airport (BLK), airport in England
- BlackRock, American investment management firm
- Burgenlandkreis (BLK), district in Saxony-Anhalt, Germany