P.O.K. (from the initial letters of Podosferikes Omades Kedrou, Greek: Ποδοσφαιρικές Ομάδες Κέντρου, English: Central Football Teams) was a coalition, a kind of athletic trust, of the three main football teams of the Attica (the "big three") which lasted until the mid 60's. The term dates to in 1927, when Olympiacos F.C., Panathinaikos F.C. and AEK Athens F.C. withdrew from the Greek Championship after disagreements with the Hellenic Football Federation (HFF), mainly over the championship's financial status. The HFF determined that league's revenues would be equally divided between all teams that participated. Olympiacos, Panathinaikos and AEK did not agree with this, and formed a group called P.O.K. During that season, they played friendly matches with each other.

The name P.O.K. is currently used to allude to the continuing dominance of the three clubs in the National A Division. Rarely does a team outside these three finish in the top three spots of the Championship; doing so is called "breaking the P.O.K.". Since 1928, only three other teams - Aris F.C., Athlitiki Enosi Larissa F.C. and PAOK FC - have won the Greek Championship. Finally, on March 7, 1963, the POK officially ceased to exist. The entry of the teams in the bulletins of PRO-PO, the establishment of the A 'national category and the participation of the Greek teams in the European football cups, made this institution weaken and finally to be abolished.