Pierre-Gabriel Marest (sometimes Maret, Marais) (October 14, 1662—September 15, 1714, Kaskaskia (Randolph County, Illinois)) was a French Jesuit missionary in Canada.
He entered the novitiate in October 1681 in Paris. For the next six years he was an instructor at Vannes. Then followed a few years of additional studies in Bourges and Paris.
In 1694 Marest was sent to Canada and chosen chaplain of an expedition under Pierre Le Moyne d'Iberville that was being outfitted to try to take the Hudson Bay region from the English. This was "contrary to my inclinations" he wrote, since he was anxious to work among the Indians.
The expedition sailed from Quebec on August 10 of that year in two frigates, the Poli and the Salamandre. Marest wrote a running account of the voyage. Near the end of August they reached the entrance to Hudson Bay. On September 24 they entered the Nelson (Bourbon) River, next to the mouth of the Hayes (Sainte-Thérèse) River. The English had built York Fort at the mouth of the latter river. The Poli anchored on the Nelson and the Salamandre, with Iberville and Marest, on the Hayes. The Salamandre was "near being lost" according to Marest before finally anchoring.
On October 13 the French were ready to bombard the fort. They asked the English to surrender. On the 14th, the English, led by Thomas Walsh, brought a list of their conditions, written in Latin by the English minister, Thomas Anderson. Marest translated the conditions for the French, the English surrendered, and the French took possession of the fort. They renamed it Fort Bourbon. Marest said a thanksgiving mass.
During the long winter, the French, including Marest, developed scurvy. Marest busied himself learning the native language, apparently from word lists supplied him before his arrival. He wrote a dictionary and translated the sign of the cross, some prayers and the Ten Commandments.