Guido Menasci (24 March 1867 – 27 December 1925) was an Italian opera librettist.
His best-known work is Cavalleria rusticana written with Giovanni Targioni-Tozzetti. He also provided the libretti for Mascagni's I Rantzau, Zanetto, for Umberto Giordano's Regina Diaz and Viktor Parma's Stara pesem (Old Song).
Menasci was born and died in Livorno.