This Notice of Funding Opportunity (NOFO) announces the availability of funds and solicits applications from eligible entities to incentivize and accelerate the upgrading or retirement of the nations legacy diesel engine fleet. Eligible activities include the retrofit or replacement of existing diesel engines, vehicles, and equipment with the EPA and California Air Resources Board (CARB) certified engine configurations and verified retrofit and idle reduction technologies.Applications will be accepted from federally recognized Tribal governments (or intertribal consortia), Alaska Native Villages, or government agencies of the U.S. Virgin Islands, Guam, American Samoa, and Commonwealth of the Northern Mariana Islands, which have jurisdiction over transportation or air quality. The EPA anticipates awarding a total of approximately $9 million under this NOFO: $8 million for Tribes and $1 million for territories. The EPA anticipates awarding approximately twelve (12) to eighteen (18) grants or cooperative agreements to Tribal governments (or intertribal consortia) or Alaska Native Villages and three (3) to five (5) grants or cooperative agreements to territory government entities, subject to the availability of funds, the quantity and quality of applications received, and other applicable considerations.