Genetically modified maize (corn) has been deliberately genetically modified (GM) to have agronomically desirable traits. Traits that have been engineered into corn include resistance to herbicides and resistance to insect pests, the latter being achieved by incorporation of a gene that codes for the Bacillus thuringiensis (Bt) toxin. Hybrids with both herbicide and pest resistance have also been produced. In 2009, transgenic maize was grown commercially in 11 countries, including the United States (where 85% of the maize crop was genetically modified), Brazil (36% GM), Argentina (83% GM), South Africa (57% GM), Canada (84% GM), the Philippines (19% GM) and Spain (20% GM).

Corn varieties resistant to glyphosate herbicides (Liberty and Roundup) have been produced. Pioneer Hi-Bred has marketed corn hybrids with tolerance to imidazoline herbicides under the trademark "Clearfield" - though in these hybrids, the herbicide-tolerance trait was bred without the use of genetic engineering. Consequently, the regulatory framework governing the approval, use, trade and consumption of transgenic crops does not apply for imidazoline-tolerant corn.^{[not specific enough to verify]}