The Eagles took an unassailable eight-point lead over arch-rivals Porto who have only two games left to play.
Benfica, whose coach Rui Vitoria spent four years at Guimaraes, quickly settled their nerves when Franco Cervi and Raul Jimenez put them 2-0 ahead after only 16 minutes.
Pizzi added the third after a one-two with Jonas and an emphatic finish and Jonas himself lobbed the fourth before halftime as Guimaraes, who had won their last seven league games, were blown away.
Jonas added the fifth from a penalty midway through the second half to complete the rout.
(Writing by Brian Homewood, editing by Pritha Sarkar)
