Helios, more fully the Helios New Encyclopedic Dictionary (Greek: Νεώτερο Εγκυκλοπαιδικό Λεξικό Ηλίου or: Νεώτερον Εγκυκλοπαιδικόν Λεξικόν Ήλιος), is a general knowledge Greek encyclopaedia. Its publication commenced in 1945 while its second edition was completed in 1960, comprising 18 volumes.