Susan Lynne Bayh (/baɪ/ BY;^[2] November 28, 1959 – February 5, 2021) was an American attorney and First Lady of Indiana from 1989 until 1997. She was married to Evan Bayh, a Democratic Indiana politician, who served as the state's governor (1989–1997) and United States Senator (1999–2011).^[3]

A newspaper in Indiana described her as being engaged in a profession it termed "professional board member" or "professional director".^[4]

Bayh began her careers in law and business as a litigator for the Los Angeles law firms of Gibson, Dunn & Crutcher, and later for the Indiana firm of Barnes & Thornburg. In 1989, she joined the pharmaceutical division at the Indianapolis-based Eli Lilly and Company, managing the company's handling of federal regulatory issues.^[3] In 1994, she left the employ of Eli Lilly and taught at Butler University's College of Business Administration, holding the title of distinguished visiting professor.

An Indiana newspaper listed eight corporations of which Bayh was a director, as of 2006.^[4] Bayh began serving on corporate boards in 1994 and thereafter served on the boards of 14 corporations, including the insurance, pharmaceutical, and food processing industries.

Bayh earned her Bachelor of Arts degree from the University of California, Berkeley. She was a past Miss Southern California and a member of Alpha Phi. She earned her Juris Doctor degree from the University of Southern California Law School in 1984.^[3]

Bayh and her husband had twin sons, Birch Evans IV (Beau) and Nicholas, born in 1995.^[5]

In May 2018, Bayh underwent brain surgery to remove a malignant glioblastoma tumor.^[6][7][8] She died in McLean, Virginia, on February 5, 2021, at the age of 61.^[9]