Zhang Qian (張騫) was an imperial envoy in the 2nd century BCE, during the time of the Han Dynasty. He was the first official diplomat to bring back reliable information about Central Asia to the Chinese imperial court, then under Emperor Wu of Han, and played an important pioneering role in the Chinese colonisation and conquest of the region now known as Xinjiang. Zhang Qian's accounts of his explorations of Central Asia are detailed in the Early Han historical chronicles ("Shiji", or "Records of the Great Historian"), compiled by Sima Qian in the 1st century BCE .