US supporters of Zundel opposed his extradition to Germany
Ernst Zundel, 65, arrived in Germany on Tuesday and was immediately taken into custody by German authorities.
Germany was able to seek his extradition on the grounds that he was running a web site denying the existence of the Holocaust.
Zundel once described Adolf Hitler as a "decent and very peaceful man".
Last week, a Federal Court judge ruled the his anti-Semitic and hatred-inciting activities were "not only a threat to Canada's national security, but also a threat to the international community of nations".
'Hero'
It took Canadian authorities two years to establish whether Zundel, who authored a book called "The Hitler we loved and why", posed a security threat.
During that time, he was being held in near-solitary confinement.
Denying the Holocaust is a crime in Germany, where Zundel's theories could be easily accessed and read through the Internet.
This enabled authorities there to open a case against him.
Zundel, who was born in Germany, moved to Canada in the late 1950s.
In 1988 he was convicted of "knowingly publishing false news" after issuing a leaflet carrying the title "Did six million really die?".
But in 1992, the Supreme Court struck down the "false news" law on the grounds that it violated freedom of expression.
Zundel, who never managed to obtain Canadian citizenship, moved to the US in 2001 but was later deported back to Canada for allegedly violating immigration laws.
A group that led a campaign to have him extradited, B'nai Brith Canada, welcomed last week's verdict.
"For decades, Zundel has spewed his venom and imbued his brand of hate in a new generation of white supremacist groups that had made him a hero," the association's vice president, Frank Dimant, said in a statement.
Zundel is now expected to be kept in custody while a German judge reviews his case.
White supremacist and Holocaust denier Ernst Zündel was expelled from Canada and arrived in Germany today.  A Federal Court judge ruled that his anti-Semitic activities were "not only a threat to Canada's national security, but also a threat to the international community of nations."

In a press release given by B'nai Brith Canada, executive vice president Frank Dimant said that "For decades Zundel has spewed his venom and imbued his brand of hate in a new generation of white supremacist groups that had made him a hero ... Zundel's day of reckoning has finally come."  Canadian Jewish Congress National President Ed Morgan was quoted as saying that “this is a significant day for the Jewish community (of Canada) and for all those who treasure tolerance in a multicultural society ... Zundel’s departure demonstrates Canada’s abhorrence for those who would propagate Holocaust denial and antisemitism. It brings closure to our efforts to bring this man to justice." 

Zündel's Toronto lawyer, Peter Lindsay, said Zündel is "very disillusioned about the process and about being the victim of a secret trial, and now being deported based on evidence he's never seen."

Upon arriving in Germany, Zündel, 65, was immediately taken into custody by authorities on the grounds that he was running a web site denying the existence of the Holocaust, which is a crime in that country.  Prosecutors in the city of Mannheim have issued a warrant for his arrest according to the Associated Press.  A spokeswoman for the federal Justice Ministry, on condition of anonymity, said authorities were able to open a case against Zundel because his Holocaust-denying site can be accessed in Germany.

In 1977, Zündel founded a small press publishing house called Samisdat Publishers which issued such pamphlets as ''The Hitler We Loved'' and ''Why and Did Six Million Really Die?'' by Richard Harwood aka Richard Verrall (a British neo-Nazi leader) as well as booklets claiming that UFOs were actually Nazi secret weapons operated from secret Nazi military bases in Antarctica.  Zundel lived in Canada for 42 years as a landed immigrant.  His last two years were spent in a Toronto jail, where he was held under the Canadian security certificate law.  The law was passed after the September 11, 2001 attacks in the United States, and allows the Canadian government to hold suspects of terrorism without charge, based on secret evidence that does not have to be disclosed to a suspect or his defense.