The office of regional governor (mu 牧, zhoumu 州牧) was used between the Han 漢 (206 BCE-220 CE) and Sui 隋 (581-618) periods. It roughly corresponded to the provincial governors (xunfu 巡撫) of later times.
The term mu, literally "herdsman", is derived from the putative administrative structure of the Western Zhou period 西周 (11th cent.-770 BCE), when the nine provinces (jiuzhou 九州) were administered by a "herdsman" (musi 牧司) each. In this sense, it is still used in the ritual Classic Liji 禮記 (chapter Quli 曲禮). Other terms for the office were zhoubo 州伯, zhouzhang 州長, mubo 牧伯 or fangbo 方伯. The terms mushou 牧守 or muzai 牧宰 referred to the regional governors (administering provinces) and the governors (taishou 太守, administering commanderies).
Emperor Cheng 漢成帝 (r. 33-7 BCE) of the Han dynasty decided in 8 BCE to rename the office of the touring regional inspector (cishi 刺史) regional governor (zhoumu), but this name change was given up three years later. Governors were during the Eastern Han period 東漢 (25-220 CE) appointed in an irregular way, and in addition to the inspectors. In the very late Eastern Han, the regional governors were given the authority over the military units garrisoned in their area of jurisdiction. Governors (taishou) of commanderies, and also the regional inspectors, were subordinated to the regional governors. Many of the warlords of that time were regional governors, like Liu Biao 劉表, regional governor of Jingzhou 荊州 (approx. Hubei) or Yuan Shao 袁紹, regional governor of Jizhou 冀州 (Shanxi).
The salary of regional governors was 2,000 shi of grain (see weights and measures), and their staff resembled that of the inspectors, with recorders (zhubu 主簿) and editors (si wenshu 司文書) for documentation, assistants (zhizhong congshi 治中從事) for the supervision of administrative sectors, mounted aides (biejia congshi 別駕從事) for the control of the commanderies and districts, the distribution or orders and the supervision of bureaus, with cavaly aides (sima 司馬) for military matters, grand rectifiers (da zhongzheng 大中正) for the selection of able personnel (see nine ranks), as well as general aides (zhangshi 長史) and aides for the recording section (bucao congshi 簿曹從事).
The Northern Dynasties 北朝 (386-581) called the office sizhou mu 司州牧. It was created in 499 from that of the regional inspector (sizhou cishi 司州刺史), and had rank 2B.
During the Southern and Northern Dynasties period and the Tang period 唐 (618-907), the offices of commanders-in-chief (dudu 都督, zongguan 總管) or military commissioner (jiedushi 節度使) gained more prominence, and the office of regional governor was abolished. It was occasionally used during the Tang and Song 宋 (960-1279) periods for high officials in the local administration around the capital (like the province of Yongzhou 雍州, approx. modern Shaanxi) or as a purely honorific title for princes.
The term was still used in the Qing period 清 (1644-1911), referring to offices of the local administration, like prefects (zhizhou 知州), called zhoumu, or district magistrates (zhixian 知縣), which were called muling 牧令.