Jack Mack Guttentag (December 9, 1923 – February 6, 2024) was an American banker and academic who was a professor of finance at the Wharton School of the University of Pennsylvania.

[5] He also served as co-director of the International Housing Finance Program at the Samuel Zell and Robert Lurie Real Estate Center.

[3] Guttentag’s research included the reform of financial institutions, financial markets, and central banking institutions; innovations in monetary policy, real estate finance, housing economics, and commercial banking; and the restructuring of bank practices and lending procedures for the Federal Reserve, insurance firms, pensions groups, and savings and loan associations, including the design of unique mortgage instruments.

[6] After becoming emeritus at the Wharton School, Guttentag developed the website The Mortgage Professor[1] to help consumers navigate the home loan market more effectively.

In addition to offering a reverse mortgage shopping service on his website, Guttentag published extensive critiques of the HECM program from both a consumer and public policy standpoint.

Working with Allan Redstone, they developed an analytical system called the Retirement Funds Integrator that attempts to maximize a lifetime stream of income derived from a combination of a retiree's financial assets and the equity in their home.