Ernest Joseph "Trey" Anastasio III (born September 30, 1964) is an American guitarist, composer, and singer-songwriter best known as the lead guitarist of the rock band Phish, which he co-founded in 1983. He is credited by name as composer of 152 Phish original songs, 141 of them as a solo credit, in addition to 41 credits attributed to the band as a whole.

In addition to his work with Phish, Anastasio has released 11 solo albums. He has also been part of several side projects; these