Short answer. Fannie Mae and Freddie Mac are functionally similar GSEs that buy and securitize conventional mortgages. The key historical difference: Fannie Mae was founded in 1938 and bought from large mortgage banks; Freddie Mac was founded in 1970 to serve the savings-and-loan industry.
Fannie Mae and Freddie Mac are often referred to interchangeably as "the GSEs." Their functional roles are essentially identical today, but they have meaningful historical differences and continue to operate as separate entities.
Origin difference
- Fannie Mae — Created 1938 as federal agency; privatized 1968. Originally focused on FHA/VA loans, expanded to conventional in 1968.
- Freddie Mac — Created 1970 to serve the savings-and-loan industry's need for conventional secondary-market liquidity.
Structural similarities
Both are government-sponsored enterprises. Both buy mortgages from lenders, package them into mortgage-backed securities, and guarantee timely payment to investors. Both are in FHFA conservatorship since September 2008. Both follow similar conforming-loan-limit rules ($806,500 in 2025 standard areas).
Functional differences
Fannie Mae historically focused on retail mortgage banks; Freddie Mac on community banks and thrifts. Today, both compete for loan-purchase business from all lender types. Fannie Mae is slightly larger (~$3.6T in mortgages outstanding vs. Freddie Mac's ~$3.2T as of 2024), and Fannie Mae's Desktop Underwriter is the more widely-used automated-underwriting system (Freddie Mac's equivalent is Loan Product Advisor).
Why two GSEs?
The two-GSE structure was deliberately designed to create competition in the secondary mortgage market. In practice, the two GSEs have followed nearly identical practices for 50+ years, and their differences are largely operational rather than substantive. Various proposals have suggested merging them, but the political consensus on conservatorship reform has been elusive.
Sources
U.S. Census Bureau Survey of Construction; National Association of Realtors Existing Home Sales report; Freddie Mac Primary Mortgage Market Survey; National Bureau of Economic Research Business Cycle Dating Committee.