Pierre Malcom Guay (March 26, 1848 – February 19, 1899) was a physician, surgeon and political figure in Quebec. He represented Lévis in the Canadian House of Commons from 1885 to 1899 as a Liberal member.
He was born in Saint-Romuald d'Etchemin, Canada East, the son of François Xavier Guay and Marie Adelaide Côté. Guay was educated at the Séminaire de Quebec and the Université Laval, where he received a M.D.. In 1874, he married Marie Louise Antoinette Roy. He served on the town council for St-Romuald d'Etchemin and was mayor from 1886 to 1887. Guay was also a governor of the board of physicians and surgeons for Quebec. He was first elected to the House of Commons in an 1885 by-election held after Isidore-Noël Belleau was unseated following an appeal. Guay died in office at the age of 50.