mb, Mb, and MB may stand for:
- Manitoba
- Mercedes Benz
- a manned base
- Bachelor of Medicine (academic degree)
- Medical Board
- megabit (Mb)¹, or 1,048,576 (220) bits, or 1,000,000 bits
- megabyte (MB)¹, or 1,048,576 (220) bytes, or 1,000,000 bytes
- millibar (mb)¹, a unit of pressure equal to one hectopascal