Gingrich was 77. Cushman told The Atlanta Journal-Constitution her mother died Wednesday and said she had "multiple health issues."
While Gingrich rarely discussed her former husband, an episode she described in one interview become fodder for his detractors.
She said she was in a hospital recovering from cancer surgery when Gingrich told her he wanted a divorce, something he has denied and her two daughters dispute.
Gingrich met the future Georgia congressman and Republican presidential candidate at Baker High School in Columbus, Ga., where she taught math. The couple married in 1962 when he was 19 and she was 26.
After their divorce in 1980, Newt Gingrich married Marianne Ginther, with whom he had apparently been having an affair. He repeated the process when he began an affair with Callista Bisek, now his third wife, while still married to Ginther.
Less famous former students described Gingrich as a quiet woman and a dedicated teacher. She returned to teaching after her divorce.
"The math was in the background," Lance Ozier told the newspaper. "She was so encouraging about the things of life. She had a type of wisdom that made me think she'd been here before."