Rainer "Rai" Weiss (/waɪs/ WYSSE, German: [vaɪs]; born September 29, 1932) is a German-born American physicist, known for his contributions in gravitational physics and astrophysics.

[1][2][3] In 2017, Weiss was awarded the Nobel Prize in Physics, along with Kip Thorne and Barry Barish, "for decisive contributions to the LIGO detector and the observation of gravitational waves".

[10] In a 2022 interview given to Federal University of Pará in Brazil, Weiss talks about his life and career, the memories of his childhood and youth, his undergraduate and graduate studies at MIT, and the future of gravitational waves astronomy.

[16] Weiss brought two fields of fundamental physics research from birth to maturity: characterization of the cosmic background radiation,[3] and interferometric gravitational wave observation.

[17][18] He co-founded the NSF LIGO (gravitational-wave detection) project,[19] which was based on his report "A study of a long Baseline Gravitational Wave Antenna System".