To mark the centenary, Hollande and Merkel will lay wreaths at cemeteries holding the dead of both sides in the northeast French town.
The 1916 offensive lasted 300 days and claimed more than 300,000 lives.
Both leaders are expected to use the day of remembrance to stress the need for unity at a time when the European Union is under pressure from the migrant crisis and a possible Brexit.
Speaking on the eve of the commemorations, Merkel underlined the close ties between the neighbouring countries, often described as the twin motors of Europe.
“To be invited to these commemorations shows the extent to which relations between France and Germany are good today,” she said.
In the run-up to the ceremony, Hollande recalled the moment during the 1984 commemoration that his predecessor Francois Mitterrand and the then chancellor of West Germany Helmut Kohl joined hands during the playing of the French national anthem.
“Mitterrand’s gesture with Helmut Kohl, the hands that reached out and found each other, that’s the symbol of reconciliation,” he told French radio this week.
Now was the time for both countries’ leaders to spell out what they wanted to do for Europe at this moment, a time when the continent was in the grip of the “evil of populism”.
That appeared to be a reference to Europe’s far-right parties which have made advances in several countries, fuelled by growing concern over an unprecedented influx of migrants.
European Commission President Jean-Claude Juncker will also attend Sunday’s acts of remembrance.
– Church bells –
Hollande and Merkel will start by visiting the German military cemetery at Consenvoye, just north of Verdun.
At a lunch Sunday the two leaders will then discuss the crisis caused by the hundreds of thousands of migrants and refugees seeking refuge in Europe and the June 23 British referendum on whether or not to quit the European Union.
Both leaders will give short speeches that will touch on the current challenges facing Europe.
Then they will attend a ceremony at the Douaumont ossuary, where the remains of 130,000 soldiers, French and German, lie underground.
It was here that Mitterrand and Kohl made their symbolic gesture to reaffirm Franco-German friendship.
Douaumont was a key strategic fort which saw heavy fighting during the battle as the French fought to recapture it.
Sunday’s ceremony at Douaumont will also feature more than 3,000 children from France and Germany in a presentation choreographed by the German film-maker Volker Schloendorff.
Church bells for miles around will ring out in memory of the soldiers who died on both sides.
Verdun was the main battle of the war for the French, and became a symbol of the war’s devastation.
German forces launched an offensive on February 21, 1916 and tried to bleed the French army dry to force Paris to the negotiating table.
French general Philippe Petain rallied his troops to contain the German drive and win back most of the terrain given up in early fighting.
The battle lasted until December 18 at a staggering cost of at least 770,000 dead, missing or wounded.
Source: Verdun (France) (AFP)