Bain & Co. founder Bill Bain dies at age 80

Mitt Romney and William Bain.

William Bain Jr., a management consultant who started two Boston firms that became influential shapers of businesses across the globe and who helped propel the business career of former governor Mitt Romney, died Tuesday at his home in Naples, Fla. He was 80.

The death was confirmed by his family, through the Chapman Cole & Gleason funeral home. No cause of death was provided.

Mr. Bain started his career helping businesses as a partner at Boston Consulting Group. With a handful of BCG colleagues, he started a rival firm, Bain & Co., in 1973. It became one of the biggest consulting firms, in part by focusing not just on providing advice but also helping clients implement a particular strategy.