They will demand "an end to the negotiations with the USA for TTIP and the non-ratification of the CETA treaty negotiated with Canada," claiming that "both agreements hollow out democratic rights and would lower ecological and social standards," organizers announced in a press release.
Five special trains and 600 buses have been laid on to bring demonstrators from all over the country to the capital, where they will march from Hauptbahnhof (main train station) through Berlin's government quarter and the Tiergarten.
Organizers say the demo represents a broad coalition of more than 30 civil society groups, including environmental, social, cultural and consumer activists, trade unions, civil rights and church organizations.
Those member groups range from anti-capitalist Attac to the German Trade Unions Federation (DGB) and the Paritätische Wohlfahrtsverband federation of care organizations.
Fear of falling standards
TTIP has been the subject of complex, secretive negotiations between the European Commission and the US government since July 2013.
Proponents say that creating the world's biggest free-trade area, removing trade barriers and harmonizing standards would boost economies and create wealth and jobs on both sides of the Atlantic.
But critics say trade is already strong between Europe and the USA at around €2 billion per day – and fear that standards for food safety, consumer protection and other areas will fall if the agreement goes ahead.
DON'T MISS: Our favourite protected German regional foods
And a particular bone of contention is the inclusion of so-called Investor-State Dispute Settlement (ISDS) - a mechanism which allows companies to bypass ordinary courts and go to an arbitration tribunal if a government violates their rights.
Earlier this week, an anti-TTIP petition signed by more than three million people all across Europe –almost half of them from Germany – was handed in to the European Commission.