The probe, the Chang'e-4, is expected to make the first-ever soft landing on the far side of the Moon, according to Xinhua.
Previous spacecraft have seen the far side of the Moon, but none has landed on it.
The Moon is tidally locked to Earth, rotating at the same rate that it orbits our planet, so the far side is never visible from Earth.
Advancing China's space programme has been a priority of its leaders, with President Xi Jinping calling for China to establish itself as a space power.
At 2:23 am (1823 GMT Friday), a Long March-3B rocket, carrying the probe including a lander and a rover, blasted off from the satellite launch centre Xichang in southwest China, Xinhua said.
China aims to catch up with Russia and the United States to become a major space power by 2030. It is planning to launch construction of its own manned space station next year.
However, while China has insisted its ambitions are purely peaceful, the US Defense Department has accused it of pursuing activities aimed at preventing other nations from using space-based assets during a crisis.