Matthew of Alsace (c. 1137–1173) was the count of Boulogne from 1160. He was the second son of Thierry, Count of Flanders and Sibylla of Anjou. Matthew forcibly abducted the nun Marie I of Boulogne and constrained her into marriage, claiming the title of Count of Boulogne jure uxoris in 1160. The forced marriage was opposed by the Church and finally annulled in 1170, but he continued to rule as count until his death.
Matthew and Marie had two daughters: Ida and Matilda. In 1171, Matthew married Eleanor of Vermandois; they had one short-lived daughter.
Matthew was a supporter of Henry the Young King, and received lands in England. He died fighting at the siege of Driencourt, during the 1173–74 revolt of the sons of King Henry II of England, under the leadership of Matthew's brother Count Philip I of Flanders. Wounded by a crossbow bolt, he did not recover.