The telescope dwarfs the Arecibo Observatory in Puerto Rico, with twice the sensitivity and a reflector as large as 30 football fields.
The decades-long hunt for signs of alien life may get a boost after the world's largest radio telescope began operating in southwestern China on Sunday.
State-run Xinhua news agency reported the 500-metre Aperture Spherical Radio Telescope (FAST), located in the mountainous region of Guizhou, was built at a cost of $180 million.
The telescope dwarfs the Arecibo Observatory in Puerto Rico as the world's largest single-dish radio telescope, with twice the sensitivity and a reflector as large as 30 football fields.
Comprising 4,450 panels, FAST's vast dish will search for signs of intelligent life and distant pulsars – tiny, rapidly spinning neutron stars believed to be the products of supernovas.
Chinese President Xi Jinping celebrated the launch and sent a congratulatory letter to the scientists and engineers who contributed to its creation, according to AFP.
Yan Jun, head of China's National Astronomical Observation (NAO), was quoted as saying that the telescope represents a leap forward for China's astronomical capabilities and will be one of several "world-class" telescope projects launched in the next decade.
Human quest for extraterrestrial signals
Scientists have been hunting for intelligent extraterrestrial life for six decades, pointing radio telescopes at stars in the hope of discovering signals from other civilisations, but have not yet found any evidence for its existence.
Last month a "strong signal" detected by a Russian telescope searching for such evidence stirred interest among scientists, but experts said it was far too early to draw conclusions about its origin.
But the new FAST telescope could "lead to discoveries beyond our wildest imagination," Douglas Vakoch, president of METI, a group seeking to send messages to space in search of alien life, told Xinhua news agency.
The construction of FAST began in 2011 and local officials relocated nearly 10,000 people living within five kilometres (three miles) to create a quieter environment for monitoring. Cell phones in the area must be turned off to maintain radio silence.