Who is madam butterfly?

"Madama Butterfly" is an Opera (1904) by Giacomo Puccini based on a play by David Belasco. The plot revolves around an American naval officer who falls in love with a geisha girl during an early visit of the U.S. Navy to Japan in the 1850s. The geisha's name is Cio-Cio-San but she is referred to as Madam Butterfly.