The Magnavox Odyssey is the world's first home video game console. It was first demonstrated on May 24, 1972 and released in August of that year, predating the Atari Pong home consoles by three years.
The Odyssey was designed by Ralph Baer, who began around 1966 and had a working prototype finished by 1968. This prototype, known as the Brown Box, is now at the Smithsonian Institution's National Museum of American History in Washington, D.C.
Source: Wikipedia, "Magnavox Odyssey", available under the CC-BY-SA License.