Guglielmo Andreoli (9 January 1862 - 26 April 1932) was an Italian pianist, music teacher and composer.
From 1876 he studied at the Milan Conservatory with Polibio Fumagalli (organ), Giovanni Rampazzini (violin) and Antonio Bazzini (composition).
In 1877-1887, he assisted his brother Carlo in organizing a series of 96 symphonic concerts called the Società dei Concerti Sinfonici Popolari.
He also published a textbook of harmony (1898, in collaboration with Edgardo Codazzi) and oversaw the release of the Italian music pedagogy at the European level of theoretical training.
[1] A music school in his hometown Mirandola is named in honor of the Andreoli brothers.