Konrad von Thüringen (English: Conrad of Thuringia) (ca. 1206 – 24 July 1240) was the fifth Grand Master of the Teutonic Knights, serving from 1239 to 1240. A Landgrave of Thuringia from 1231 to 1234, he was the first major noble to join the military order.
Conrad was the youngest son of Hermann I, Landgrave of Thuringia, and Sophia, a daughter of Otto I, Duke of Bavaria. His elder brother Louis IV of Thuringia was married to Saint Elisabeth of Hungary. When Louis died in 1227 during the Sixth Crusade, his brother Henry Raspe became regent for Louis' minor son Herman II, and Conrad took on the title of Count of Gudensberg in Hesse, assisting his brother in ruling the area.
On Elisabeth's death in 1231, Henry Raspe took Thuringia for himself, and together with Conrad, worked to consolidate power. Conrad engaged in battle a number of times with Siegfried III, Archbishop of Mainz, at one point personally swinging him around and threatening to cut him in two. In 1232, he besieged the city of Fritzlar, massacring its populace and burning the church.
Elisabeth had founded a hospital in Marburg and had intended to bequeath it to the Johanniter Order, but this was rejected by her defensor, Conrad of Marburg. Pope Gregory IX sent a commission to settle the matter, and it decided in favor of Conrad of Marburg on 2 August 1232. In the summer of 1234, Conrad travelled to Rome and convinced the Curia to turn the hospital and parish church in Marburg over to the Teutonic Knights, which had founded a house in the city the previous year. In November, Conrad set aside his temporal title and entered the Teutonic Order himself. The next year, he joined the commission to Rome that represented his sister-in-law in the canonization process, and he remained in the court of the Pope until Pentecost of 1235 when she was declared a saint.