The module, named "Tianhe", or "Harmony of the Heavens", was launched on the Long March 5B, China's largest carrier rocket, at 11:23 a.m. (0323 GMT) from the Wenchang Space Launch Centre on the southern island of Hainan.
The launch is the first of the planned 11 missions that is set to put the space station into shape.
China's space programme has also recently brought back the first new lunar samples in more than 40 years and expects to land a probe and rover on the surface of Mars later next month. For 29 days. In July 2019, China allowed Tiangong 2 to burn in a controlled manner after almost three years.
The European Space Agency has sent astronauts to China to receive training in order to be ready to work inside the Chinese space station once it is launched.
Minutes after the launch, the fairing opened to expose the Tianhe atop the the core stage of the rocket, with the characters for "China Manned Space" emblazoned on its exterior.
The completed station will be similar to the Soviet "Mir" station that orbited Earth from the 1980s until 2001. Three astronauts are now preparing to fly to Tianhe aboard the Shenzhou 12 spacecraft, possibly in June.
April 20, 2017: China's first cargo resupply spacecraft, the Tianzhou-1, or "Heavenly Vessel", was launched.
If the ISS were to cease operating in the coming years - and secure its operation until 2024 - China would likely be the only country with a space station.
The core module will give three astronauts 50 cubic meters of living space, equipped with advanced telecommunications equipment that will allow astronauts to browse websites "no differently from normal people using the internet and phones on Earth", Bai Linhou, deputy chief designer of the space station, told CCTV. While Russia and the United States are now discussing what to do with the International Space Station after 2024, the two countries are contemplating their new settlement bases in space.
Another Chinese program aims to collect soil from an asteroid, a key focus of Japan's space program. It weighs 60 tons and is expected to link to a Chinese satellite.
Thursday's launch comes as China is also forging ahead with crewless missions, particularly in lunar exploration.
China's unmanned moon mission in December carried rocks and soil sample back to Earth, making it the third country after the USA and Russian Federation to carry out this feat.
The Tianwen-1 space probe has been orbiting the red planet since February while collecting data. Thief Zhurong will search for evidence of life.
The craft was also used for medical experiments and, most importantly, tests meant to prepare for the construction of a space station. No timeline has been proposed for such projects.
China's program has advanced in a steady, cautious manner, largely avoiding the failures seen in the US and Russian efforts with their astronaut programs, moon and Mars missions when they were locked in intense competition during the heady early days of space flight.
China has proceeded in a more measured, cautious manner than the U.S. and Soviet Union during the height of the Space Race. It had major setbacks, including the Chang Zeng 5 or Long March 5 rocket that failed due to an engine problem.