Goryeo general under King Gongmin, son of Jang Jong-haeng, who was enfeoffed as Lord of Arim for defeating the Red Turbans; the reason the clan took Geochang as its seat
| Era | 고려 말 공민왕 때 |
| Clan | 거창 장씨 |
Jang Du-min (章斗民) was the son of the clan founder Jang Jong-haeng, and Wikipedia calls him the mid-founding ancestor. According to the Digital Geochang Culture Encyclopedia, as a general (sang-janggun) under King Gongmin he defeated the Red Turban bandits and was enfeoffed as Lord of Arim (娥林君), receiving the Geochang area as his fief. Arim is an old name of Geochang. His descendants settled there and took Geochang as their seat, so today's clan seat derives from his title.
A text on Geonyejeong says he distinguished himself in driving the Red Turbans out of Gaegyeong. The Red Turbans invaded Goryeo in 1359 and 1361, with Gaegyeong falling and being retaken in 1361, but which battle he fought and what he did could not be confirmed here. A record that he was a son-in-law of U Tak is also mentioned, but this is family tradition to be checked elsewhere. His dates are unknown.
In Sangnim-ri, Geochang-eup, stands the Arim-gun Sejeokbi, a stele recording his deeds, said to be written by Gwak Jong-seok. His grandson Jang Sam-jang is said to have refused office out of loyalty to Goryeo and settled at Hangi-ri, Ungyang-myeon, becoming the clan's settling ancestor in Geochang. The Geochang Jang clan later spread across Geochang and Anui.
The Digital Geochang Culture Encyclopedia says descendants settled in Geochang, the fief of Jang Du-min, and took it as their seat. His grandson Jang Sam-jang settled at Hangi-ri, Ungyang-myeon, and Sangnim-ri, Jeongjang-ri and Jangpal-ri in Geochang-eup are named as clan villages.
His tomb could not be confirmed. The Arim-gun Sejeokbi stele stands in Sangnim-ri, Geochang-eup.