The leader of the world's 1.2 billion Catholics has a gruelling schedule for the four-day stay, combining official talks with outreach to the faithful, many of whom have grown alienated during his six-year-old papacy.
The pontiff, 84, will visit the free-wheeling, overwhelmingly Protestant or secular German capital for meetings with the country's political class before addressing a capacity crowd of 70,000 at the historic Olympic Stadium.
He will also travel to Erfurt in former communist East Germany and predominantly Catholic Freiburg in the southwest, speaking to an estimated total of 260,000 people in his mother tongue before departing Sunday.
The pope, wearing long white vestments, was welcomed at Berlin's Tegel Airport with a 21-gun salute and children bearing flowers on Thursday morning. Most of Germany's political and religious elite was present to greet the 84-year-old pontiff.
"I have not come here primarily to pursue particular political or economic goals, as other statesmen rightly do, but rather to meet people and to speak about God," he said.
But as if to underline the ambivalence in his native country, dozens of leftist deputies vowed to boycott the pontiff's first-ever speech to a parliament, while throngs of demonstrators will rally a few blocks away behind police barricades.
"It will do the pope good to come to Berlin and sense what reality is in the year 2011," said the co-leader of the opposition Greens, Claudia Roth, amid accusations the address will undermine the separation of Church and state.
Benedict said on Thursday that such protests were "normal in a free society marked by strong secularism." "One can't object" to such protests, he added. "I respect those who speak out."
The 2005 election of Joseph Ratzinger, who was born in the Bavarian village of Marktl am Inn, as the first German pope for around 500 years met with an outpouring of joy in Germany.
However his papacy has been marred by revelations last year of widespread molestation by German priests over the last several decades, which helped drive more than 181,000 from the Church - 57,000 more than in 2009.
The Vatican has indicated it is likely the pontiff will meet with sexual abuse victims, as he did on trips to Ireland and Malta.
"I can understand that in the face of such reports, people, especially those close to victims, would say 'this isn't my Church anymore'," the pontiff told reporters on his plane trip from Rome.
Germany's top archbishop, Robert Zollitsch, admitted the Church had "failed" in its response to the problem of predatory clergy amid allegations the crimes were hushed up. He said he hoped the pope's stay would revitalise Catholicism in his homeland and offer orientation following the turbulence of recent years.
"The pope's visit is an opportunity to win people over who were unconvinced before," he said.
But most Germans appear largely indifferent to "their" pope coming to visit. A poll published last week showed 86 percent - including 63 percent of Catholics - thought the trip was "basically unimportant" or "totally unimportant" for them personally.
Germany's Christians are split down the middle between Catholics and Lutherans, each with about one-third of the population.
Catholic leaders hope to avert the disruption seen last month in Spain during World Youth Day celebrations, when thousands marched against the pope, sparking a police crackdown, or during a 1996 trip when John Paul II in his popemobile encountered paint bombs and a female streaker.
Critics say Ratzinger, known as "God's Rottweiler" while head of the Vatican's powerful Congregation for the Doctrine of the Faith, is out of touch with modern life with his rigorous dogma.
Organisers say at least 20,000 protesters, including gays, feminists, atheists, abuse survivors and other papal opponents will rally in Berlin.
"Our alliance is not protesting against faith but rather calls on Catholics to demonstrate against the Church's stances," said Pascal Ferror, coordinator of the collective calling itself "The Pope Is Coming."
The pope will give 18 sermons and speeches during his 21st trip abroad, his third to Germany following World Youth Day in Cologne in 2005 and a private visit to his native Bavaria in 2006.