It's the home event for Germany's mighty car industry.
And this year the Frankfurt Auto Show is all about zero-emission vehicles.
Centre stage is a new electric Volkswagen.
Chief executive Herbert Diess says the ID.3 could go on to be as significant as its legendary Golf hatchback:
(SOUNDBITE) (German) VOLKSWAGEN'S CEO HERBERT DIESS, SAYING:
"The absolute highlight is the ID.3. A typical VW car. About the size of a VW Golf, but much bigger on the inside."
Plenty of other electric vehicles are set to make their debut this week.
But it's all too little, too late for environmentalists.
In August activists vandalized forty luxury vehicles, and called for the Frankfurt show to be cancelled.
Protests are expected outside the event this week.
One group says VW can't claim to be green:
(SOUNDBITE) (German) TINA VELO, PROTEST GROUP 'SAND IN THE GEARBOX', SAYING [ABOUT THE MEETING WITH VW]:
"Mr Diess and Volkswagen adorn themselves with green clothes these days, but this is the very same company that lied to us and cheated us, which was not above using all its knowledge and art of engineering to manipulate emissions."
Regulators are watching too.
Over the next few years carbon dioxide emissions limits are set to tighten dramatically.
Manufacturers that exceed targets will face big fines.
VW says that proves it was right to invest about 88 billion dollars in becoming the biggest maker of EVs.
But electric cars are still much more expensive to make, and buy.
If consumers aren't won over, some automakers worry that zero emissions could also mean zero profits.