The oldest Nintendo video game system is the Color TV-Game 6, released June 1, 1977 in Japan by Nintendo Playing Card Co. (Nintendo's pre-video game name).
This predates the NES (Famicom) by six years and marks Nintendo's entry into the video game industry. The Color TV-Game series (6, 15, Racing 112, Block Kuzushi) sold over 3 million units combined, funding Nintendo's arcade and later console development.
Designed in partnership with Mitsubishi Electric, the Color TV-Game 6 represents the humble beginning of the company that would define gaming for decades.