Peter Ernest Cianchette (born June 25, 1961)[3] is an American diplomat, businessman, politician and former United States Ambassador to Costa Rica from 2008 to 2009.

Cianchette was the Republican nominee for governor of Maine in 2002, losing to Democrat U.S. Representative John Baldacci.

In 1985, he moved to the South Portland area and worked in business there[4] with The Cianchette Group, a public affairs management and business consulting firm; the Portland-based private investment firm, CHK Capital Partners; and, starting in 1998, the business and public affairs consulting firm, Pierce Atwood Consulting, where he served as chief operating officer and executive vice-president.

He served on the National Republican Committee and as the Maine General Chairman of the Bush-Cheney 2004 re-election campaign.

A community and civic activist, Cianchette served as a director on the boards of the Make-A-Wish Foundation of Maine and also served on the Republican National Committee and as director of the Greater Portland Big Brothers/Big Sisters, the Boy Scouts of America/Pine Tree Council, the Portland Chamber of Commerce, the Southern Maine Community College Foundation, YES!