Eva Sylvia Vrethammar (born 22 August 1945) is a Swedish traditional pop and jazz singer.

Vrethammar was born in Uddevalla, Sweden. She is the daughter of Harald Vrethammar, an education official, and Britta Vrethammar, a musical education teacher, specializing in the piano.

In 1969, she released a Swedish-language cover version of Dusty Springfield's "Son of a Preacher Man", entitled "En lärling på våran gård". Vrethammar is also fluent in English.

In the 1970s, she occasionally appeared as guest singer with the Bert Kaempfert orchestra, singing in English. After a series of tribute concerts in Germany in 2006 and 2008, where she returned to the bandleader's music with ex-Kaempfert trombonist Jiggs Whigham and other former orchestra members (playing as the HR Big Band), in 2012, she recorded numbers from the tours.

She is perhaps best known for the 1974 release, "Y Viva España," an English adaptation of the Dutch language "Eviva España," first recorded by the Belgian singer Samantha (Christiane Bervoets). It reached #4 in the UK Singles Chart in September 1974, spending over six months in the charts. The song also peaked at number #67 in Australia in 1975. She was known in the UK and Australia simply as Sylvia. Globally her version alone sold over one million copies, and was awarded a gold disc.

She took part in Melodifestivalen 2002, singing "Hon är en annan nu". She participated again in Melodifestivalen 2013 in the hope of representing Sweden in the Eurovision Song Contest 2013 which was held in Malmö. She sang her song "Trivialitet" in the fourth semifinal, which was also held in Malmö. She came seventh and was therefore eliminated from the contest.