The River Zekoi is a major body of water in Carthak. The river cuts through Carthak and further into the Southern Lands. It branches off several times into smaller tributaries, but the main river flows on.
When the Tortallan delegation arrived at the capital, Veralidaine Sarrasri jumped into the River Zekoi to save a marmoset that had been dropped in by a human child by accident. She named him Zekoi "Zek" in reference to that.