Agia Effimia Bay (Greek: Όρμος Αγίας Ευφημίας Ormos Agias Effimias) is a bay on the eastern coast of the island of Kefalonia, Greece. Its total length is approximately 5 kilometres (3.1 mi), and it is approximately 3 kilometres (1.9 mi) wide from Sami to Cape Dichalia. It is bordered by Sami Bay to the south and the Strait of Ithaca to the northeast. The mountains surround the gulf to the east, while a small valley lies in the area of the port of Agia Effimia. There is a ferry route linking Agia Effimia and the island of Ithaca. The Kissou Avlaki stream empties into the gulf, slightly west of Sami. The Sami-Agia Effimia Road surrounds the southwestern portion, while a road linking to the village to the north dominates the north.