| Chief of the Onggirat | |
| Tenure: | 12th-13th century |
| Successor: | Anchen |
| House-Type: | Clan |
| Noble Family: | Bosqur |
| Spouse: | Čotan |
| Issue: | Anchen Börte |
Dei Sechen was the chief of Onggirat tribe's Bosqur clan in 12th-13th centuries. His daughter Börte was the first and principal wife of Genghis Khan.
According to The Secret History of the Mongols Temujin was betrothed to Börte when he was 9 years old by Yesugei and Dei, when Yesugei was looking for a bride for his son.[1] Yesugei put his son in care of Dei Sechen and returned to his tribe, only to be poisoned on the road during a lunch by Tatars. However, according to Rashid al-Din, Dei Sechen wasn't happy with bethothal, it was his son Anchen (按陳) who facilitated the process.[2] Japanese researcher Mako Fujii argued that Dei Sechen was involved in Yesugei's death.[3]
Later, when Temujin grew up, he still married his betrothed Börte. Part of her dowry was a luxurious black marten, which Temujin later presented to Toghrul, thus enlisting the support of the Keraites.
He had a spouse named Chotan who bore his sons Anchen and Qogu and his daughter Börte. His descendants married into ruling Borjigin family, producing imperial son-in-laws and empresses.[4]