Marios Athanasiadis (born 31 October 1986) is a Cypriot cross-country mountain biker. At the 2012 Summer Olympics, he competed in the Men's cross-country at Hadleigh Farm, finishing in 40th place, the last rider to finish without being lapped. At the 2014 Commonwealth Games he finished in 16th place in the men's cross-country.

He took up cycling at the age of 12, introduced to it by the man who would become his coach. His gold medal at the 2009 Games of the Small States of Europe was Cyprus's first in mountain biking. He was also the Cypriot Youth Ambassador at 2010 Youth Olympic Games.