Marek Semjan (; born 7 November 1987) is a Slovak tennis player playing on the ATP Challenger Tour. On 30 August 2010, he reached his highest ATP singles ranking of 218.
He won over top seed Fernando Verdasco at the 2012 UniCredit Czech Open in ProstÃÂjov in three sets 6âÂÂ4, 6âÂÂ7 (5âÂÂ7), 6âÂÂ4.