In the United States, the Green Party has been active as a third party since the 1980s. The party first gained widespread public attention during Ralph Nader's presidential runs in 1996 and 2000. Currently, the primary national Green Party organization in the U.S. is the Green Party of the United States, which has eclipsed the earlier Greens/Green Party USA. There are Green Parties in many nations, with total membership being about a million people.

The Green Party in the United States has won elected office mostly at the local level; most winners of public office in the United States who are considered Greens have won nonpartisan-ballot elections (that is, the winning Greens won offices in elections in which candidates were not identified on the ballot as affiliated with any political party). The highest-ranking Greens ever elected in the nation were John Eder, who was a member of the Maine House of Representatives until his defeat on November 7, 2006, and Audie Bock, who was elected to the California State Assembly in 1999 but switched her registration to Independent seven months laterhttp://www.drivingmrnader.org/epilogue.htm running as an independent in the 2000 election http://www.courtinfo.ca.gov/courtadmin/aoc/documents/capcon1100.pdf. In 2005, the Party had 305,000 registered members in states that allow party registration, as well as tens of thousands of members and contributors in the rest of the country. During the 2006 elections the party had ballot access in 31 states.

Greens emphasize environmentalism, non-hierarchical participatory democracy, social justice, respect for diversity, peace and nonviolence.