Athens Urban Transport Organization (OASA) / Οργανισμός Αστικών Συγκοινωνιών Αθηνών (ΟΑΣΑ)

Since 2011, the main operator of urban transport in Athens
OSY after the merger of ETHEL and ILPAP in July 5, 2011 began to serve buses and trolleybuses of Athens and Piraeus
osy.gr : About

Operator that carries out a large percentage of OASA routes in the wider Attica region.