GLASS-z12 (formerly known as GLASS-z13) is a Lyman-break galaxy discovered by the Grism Lens-Amplified Survey from Space (GLASS) observing program using the James Webb Space Telescope's NIRCam in July 2022.

[8][9] Spectroscopic observations of GLASS-z12 by the Atacama Large Millimeter Array (ALMA) in August 2022 confirmed that the galaxy has a spectroscopic redshift of 12.117±0.012, making it one of the earliest and most distant galaxies ever discovered, dating back to just 350 million years after the Big Bang, 13.6 billion years ago.

[10][5] ALMA observations detected an emission line associated with doubly ionized oxygen (O III) at 258.7 GHz with a significance of 5σ, suggesting that there is very low dust content in GLASS-z12, if not the early universe as well.

[11][12] GLASS-z12 derives its name from the GLASS survey that discovered it and its estimated photometric redshift of approximately z = 12.4+0.1−0.3.

[5] However, due to the expansion of the universe, its present proper distance is 33.2 billion light-years.