She succeeds G. Allen Andreas, who remains chairman.
Woertz, 53, joins the company from the oil company Chevron Corp. (CVX), where she most recently served as executive vice president in charge of operations that included refining, marketing, lubricant, supply and trading businesses in 180 countries.
Decatur-based ADM is one of the world's largest processors of oilseeds and corn.
Its corn-processing division makes syrups, sweeteners, citric and lactic acids, ethanol and other products. The oilseeds division produces vegetable oils, animal feeds, and emulsifiers.
For its latest fiscal year ended in June, ADM earned $1.04 billion, or $1.59 per share, on revenues of $35.9 billion.