A type of mortgage loans (mortgages) that constitute securitized residential mortgage loans guaranteed by a certain government agency. Such mortgages (an individual mortgage or a collection of mortgages) are used to secure (i.e., back) an asset-backed security (ABS)- specifically, mortgage-backed security (MBS)- issued by government agencies- in the US, federal agencies such as Fannie Mae, Freddie Mac and Ginnie Mae.

Agency mortgage loans are mortgages sold to, guaranteed or insured by, and/ or pooled by any agency to secure or otherwise support any type of mortgage pass -through security, collateralized mortgage obligation (CMO), REMIC or other types of securities issued or guaranteed by such agency.