榆林市
Li Sigong (李思恭) (d. 886?), né Tuoba Sigong (拓拔思恭), formally the Duke of Xia (夏公), was a Tangut warlord of the late Tang dynasty, who, for his contributions against the rebel Huang Chao, was installed as Dingnan Jiedushi (定難, headquartered in modern Yulin, Shaanxi) as its military governor ("Jiedushi"). The position was hereditary and passed down through his family, eventually becoming the fully independent Tangut state of Western Xia from the 11th to 13th centuries.