2B or 2-B may refer to:
Science
- IARC group 2B
- Type IIB string theory, a physical theory about the basic substance of the universe
- II-b or IIb, a subtype of Type II supernova
- Transcription factor II B, a type of protein structure
- Type IIb diamond, a classification of natural diamonds
- Alpha-2B adrenergic receptor, a type of protein structure
Sports and entertainment
- 2B (band), a Portuguese band
- 2B (film), a 2009 science fiction film
- 2B (Nier: Automata), the video game's main protagonist
- 2b Theatre Company, a theatre company in Halifax, Nova Scotia
- 2b2t, а Minecraft server with no rules
- Second baseman, a fielding position in baseball
- Double (baseball), a type of base hit
Other uses
- 2B lead, a grading of pencil hardness
- Aerocondor, IATA airline code 2B
- Haute-Corse, French department 2B (northern Corsica)
- Stalag II-B, a prisoner of war camp in Germany