Adam Guy Riess (born December 16, 1969) is an American astrophysicist and Bloomberg Distinguished Professor at Johns Hopkins University and the Space Telescope Science Institute.

In July 2016, Riess was named a Bloomberg Distinguished Professor at Johns Hopkins University for his accomplishments as an interdisciplinary researcher and excellence in teaching the next generation of scholars.

The team's observations were contrary to the existing theory that the expansion of the universe was slowing down; instead, by monitoring the color shifts in the light from supernovae from Earth, they discovered that these billion-year old novae were still accelerating.

[12] The discovery of the accelerating universe was named 'Breakthrough of the Year' by Science magazine in 1998,[13] and Riess was jointly awarded the 2011 Nobel Prize in Physics along with Schmidt and Perlmutter for their groundbreaking work.

[15][16] Riess received the Astronomical Society of the Pacific's Robert J. Trumpler Award in 1999 and Harvard University's Bok Prize in 2001.

[17] In 2006, he shared the $1 million Shaw Prize in Astronomy with Saul Perlmutter and Brian P. Schmidt for contributions to the discovery of the acceleration of the universe.

[19] Along with Perlmutter and Schmidt, he was awarded the 2011 Nobel Prize in Physics for his contributions to the discovery of the acceleration of the expansion of the universe.

[18] Riess, along with Brian P. Schmidt, and the High-Z Supernova Search Team shared in the 2015 Breakthrough Prize in Fundamental Physics.