Ursula Haverbeck-Wetzel was sentenced to ten months in prison by a Hamburg court, convicted of incitement of hatred for statements she made denying the Holocaust, German media reported on Thursday.
The Holocaust is "only a belief," said Haverbeck-Wetzel, dubbed Nazi-Oma (Nazi grandma) by the media on Friday.
She already has a criminal record with two fines and a suspended sentence for sedition.
Haverbeck-Wetzel was dragged back into court after she went on television in April to declare to NDR reporters that "the Holocaust is the biggest and most sustainable lie in history".
Unapologetic for her comment, she had told the court cheerfully, "yes I said that indeed", according to media reports.
In Germany, the crime of incitement of hatred refers to actions that encourage hatred or violence towards a group of people because of their religion, race or ethnic background. It also punishes any individual who publicly "approves of, denies or downplays" the actions of the Nazis which violated international law by up to five years in prison.
More than 1 million people, most of them European Jews, died at the Auschwitz-Birkenau camp between 1940 and 1945 before Soviet forces liberated the site.
Haverbeck-Wetzel was indicted in Hamburg because that is the headquarters of NDR, according to the Hamburger Abendblatt.
The 87-year-old is a known member of the extreme right-wing scene in Germany, according to the Süddeutsche Zeitung. In 2004 she helped to found an association that helped people who were "persecuted" for denying the Holocaust.
Haverbeck-Wetzel was also once chair of the "Collegium Humanum," which started as an environmental group, but became a right-wing extremist organization and was banned by the German government.
During her own trial, members of the nationalistic, right-wing National Democratic Party of Germany (NPD) supported Haverbeck-Wetzel with applause and flowers, according to the Hamburger Abendblatt.
Haverbeck-Wetzel has said she will appeal the verdict.