The Tianlai project is an experiment aimed at detecting dark energy by measuring the baryon acoustic oscillation (BAO) features in the large scale structure power spectrum, which can be used as a standard ruler. The basic plan is to build a radio telescope array, and use it to make 21cm intensity mapping observations of the neutral hydrogen which traces out the large scale structure of matter distribution.

Currently, the Tianlai collaboration includes scientists and engineers from China, Canada, France, and USA.

The word "Tianlai" literally means "heavenly sound", it was coined by the ancient philosopher Zhuangzi (or Chuang Tzu, 369BCE-286BCE) .