East Sister Island is a 15 hectare island in Ontario, Canada, located within Lake Erie.

It has no long-term human population and is maintained as a Provincial Nature Reserve.

The island has become the home of a breeding colony of double-crested cormorants.

[3] The forests of the island are dominated by the common hackberry and Kentucky coffeetree.

[4] Unusual species on the island include the wild hyacinth[5] and the Lake Erie water snake, Nerodia sipedon insularum.