Sega Genesis, video game system, 16-bit. Introduced in 1989, the first game was Altered Beast, later known for the game Sonic the Hedgehog, which became the icon for which Sega was known, similar to the Taco Bell dog.
This was the first true 16-bit console system, not to be confused with the TurboGrafx 16. It's biggest competition came from the Super Nintendo, or SNES, which came out in 1990.
There were 8 games released in 1997, and no more after that date. The Genesis had the add-on of the Sega CD.
Also see:

Sega GameGear Portable
Sega Master System Original Sega System
Megadrive Japanese Genesis
Sega CD Genesis add-on
Sega Saturn 32-bit
Dreamcast latest and greatest as of 2000