Eleftherios "Lefteris" Kosmidis (Greek: Ελευθέριος "Λευτέρης" Κοσμίδης; born 6 May 1991) in Greece is an international elite artistic gymnast and a former world champion on Men's Floor Exercise.

He went on to compete at the World Cup Grand Prix in Glasgow, winning two medals: silver in the floor exercise and bronze on Vault.

In 2008, Kosmidis became Junior European champion on the Men's Floor Exercise ahead of Christian Bazan and Daniel Keatings with a score of 15.525.

In the final competition he won a Gold medal on Floor with a score of 15.700, beating All-Around champion Kohei Uchimura and Daniel Purvis.

In 2011 he failed to qualify for the Floor Exercise final at the World Championships in Tokyo, coming in 10th place in the qualification round.