Olympiacos-Panathinaikos and Fenerbahce-Galatasaray derbies have much in common. They involve the two most successful and popular clubs in their respective countries; they divide football-impassioned cities; and they are widely considered among the biggest rivalries across the world.

With their latest instalments taking place on Sunday, FIFA.com wants to know whether you consider the principal derby in Athens or Istanbul to be the biggest.

There is no denying the magnitude of a fixture known as the 'Derby of eternal enemies' and the 'Mother of all battles'. Olympiacos and Panathinaikos have, between them, seized 55 of 72 Greek league crowns, meaning there is invariably more than just intense pride at stake when they collide.

Fenerbahce were founded in 1907, only two years after Galatasaray. The cross-city enemies are divided by the Bosphorus sea, but not by Turkish Super Lig titles: they have won 17 apiece, an equipoise which fuels their vehement rivalry.

So, it's over to you: is the Olympiacos-Panathinaikos or Fenerbahce-Galatasaray derby the biggest? Click 'Add your comment' to make your opinion known, remembering to keep your posts clean, respectful, about the topic and in English.