A megabit is an SI-multiple (see prefix mega) of the unit of bit for digital information storage or transmission. The International Electrotechnical Commission's standard IEC 60027 specifies the symbol to be Mbit, but Mb is also in common use.

1 megabit = 1000² bits = 10⁶ bits = 1000000bits.

Based on an eight-bit-sized byte this is equal to 125000bytes, 125 kilobytes (kB), or approximately 122 kibibytes (KiB).

The megabit is commonly used when referring to data transfer rates of computer networks or telecommunications systems, e.g., a 100 Mbit/s (megabit per second) Fast-Ethernet connection, or a 10 Mbit/s Internet access service.

The binary-interpreted counterpart of the megabit, the mebibit (Mib), refers to the quantity of 10242 bits = 1048576bits.