Thomas Grant Gustin is an American actor and singer. He is best known for his roles as Barry Allen / The Flash on The CW series The Flash (2014–2023) as part of the Arrowverse, and as Sebastian Smythe on the Fox series Glee. Trained in musical theater, his first major credit was as part of the 2010 national tour of West Side Story; he returned to theater in the original Broadway production of Water for Elephants, originating the starring role of Jacob Jankowski.

Barry Allen, also known by his alter ego The Flash, is a fictional character in The CW's Arrowverse franchise, first introduced in the 2013 episode "The Scientist" of the television series Arrow, and later starring in The Flash. The character is based on the DC Comics character of the same name, created by Robert Kanigher and Carmine Infantino and was adapted for television in 2013 by Greg Berlanti, Andrew Kreisberg and Geoff Johns. Grant Gustin portrayed Barry Allen, with Logan Williams and Liam Hughes portraying younger versions.