Heinrich I von Müllenark (also Mulnarken) (1190–1238) was the Archbishop of Cologne within the Holy Roman Empire from 1225 until 1237.
Heinrich set out immediately to punish the conspirators in the murder, and he received necessary rights and equipment from the Holy Roman Emperor, Frederick II, and Pope Honorius III.
A bounty of 2,000 silver marks was placed on the head of the lead conspirator, Frederick I of Isenberg, and his castles were besieged and captured.
After travelling to Rome to have his excommunication lifted, Frederick was captured in Liège and sold to Cologne, where he was executed on 14 November 1226 at the Severin Gate.
He was forced to concede the weakness of the prince-bishopric, and he had to recognise municipal rights on several Westphalian towns.