Gamble made the announcement to the faculty, staff, and student leadership of the university at a morning meeting that was followed by an e-mailed letter to the entire campus.
Gamble and his wife, Patricia, had decided several years ago that he would end his 25-year career as an administrator in 2009. He came to MSU in December 2000.
Their decision was reinforced by Patricia Gamble's diagnosis with breast cancer in 2008, the declining health of his 87-year-old mother and the birth of a new grandchild in January, said Gamble, who will be 67 in June.
Patricia Gamble has received treatment and is in good health. The couple plans to spend more time with family and traveling around the state. Gamble, who holds a doctorate in linguistics, also plans to teach one or two courses annually in MSU's Department of Sociology and Anthropology.
"In retirement, you'll still see me around campus," Gamble said in his letter.
Montana Commissioner of Higher Education Sheila Stearns will conduct a search for Gamble's successor on behalf of the Montana Board of Regents. Gamble will stay in office until new leadership is found, even if that carries him into 2010, he said.
Gamble is MSU's 11th president.
Before coming to MSU, Gamble was the provost and senior vice president at the University of Vermont and served as its chief academic and operating officer.
Prior to Vermont, Gamble was a professor of anthropology at Washington State University. During his tenure at WSU, Gamble served as interim provost for one year and vice provost for five years.
Gamble is the author of two books and a dozen articles on Native American languages. He holds a doctorate in linguistics from the University of California, Berkeley.