John B. Neff (September 19, 1931 – June 4, 2019) was an American investor, mutual fund manager, and philanthropist.

[1] Windsor became the highest returning, and subsequently largest mutual fund in existence during Neff's management, eventually closing to new investors for a period in the 1980s.

He then worked at the National City Bank of Cleveland before attending the School of Business at Western Reserve University, graduating in 1958.

After three years at the company, he was appointed portfolio manager of the Windsor, Gemini, and Qualified Dividend funds.

One area in which Neff was similar to value investors such as Warren Buffett was in his emphasis on return on equity (ROE), stating that it is the single best measure of management effectiveness.