Green Tortoise Adventure Travel is an American long-distance tour bus company founded by Gardner Kent in mid-1973[1][2] and based in San Francisco, California.

[1][3] Although the two companies were very similar, Grey Rabbit put more emphasis on making the journey time short – e.g. San Francisco to New York in less than four days – whereas Kent planned a service that would be a little slower[3] but more relaxed, with more stops (for swimming, picnics, etc.)

[5] In a 1982 article in The Sunday Oregonian, a reporter for the Field News Service wrote that, "The hippie bus companies may have been known for speed but never comfort.

Buses were old, overcrowded and prone to breakdowns – frequently stranding their generally hirsute passengers in the often highly unsympathetic hinterlands.

In 1979, Green Tortoise lengthened its cross-country journey time to seven days and began focusing more on tour bus service than on transportation.

Itineraries typically try to avoid heavily touristed locations, and prioritize places of natural and cultural interest such as national parks, monuments, forests, hot springs, or archaeological ruins.

Green Tortoise has historically made trips to destinations in the United States including Alaska and regular summer coast-to-coast routes from San Francisco to Boston and back.

The company discontinued its regularly scheduled service between San Francisco and Seattle via Eugene and Portland in 2001, in favor of focusing on "adventure camping trips".