According to Official Guinness Records,
The largest Greek folk dance was achieved by 5,614 people in an event organised by EKPOL, the Social and Cultural Council of the Prefecture of Magnesia, in Volos, Thessaly, Greece, on 31 August 2012. In achieving this record they simultaneously achieved the record for "Largest sirtaki dance", as that was their dance of choice.
For a complete list of 2012 records, please visit 2012 Guinness Records in Greece.