Guilherme Roth dos Santos (born 11 October 1982 in Caxias do Sul) is a Brazilian competitive swimmer.

[7] He joined the Brazilian national delegation who attended the 2009 World Aquatics Championships in Rome, where he competed in the 4×100-metre freestyle, along with César Cielo, Fernando Silva and Nicolas Oliveira.

The team finished the final in fourth place, with a time of 3:10.80, South American record.

[8][9][10] At the 2010 South American Games, Roth won the silver medal in the 4×100-metre freestyle.

[11] Participating in the 2012 FINA World Swimming Championships (25 m) in Istanbul, he went to the 4×100-metre medley final, finishing 4th,[12] and the 4×100-metre freestyle final, finishing 6th.