Eridania Lake is a theorized ancient lake on Mars with a surface area of roughly 1.1 million square kilometers. It is located at the source of the Ma'adim Vallis outflow channel and extends into Eridania quadrangle and the Phaethontis quadrangle. As Eridania Lake dried out in the late Noachian epoch it divided into a series of smaller lakes.
References
Eridania Lake Wikipedia(Text) CC BY-SA