Mander

The Mander is a river in Game of Thrones. It is the largest river in the Reach, the region ruled by House Tyrell of Highgarden. It flows west through the Reach from headlands near Tumblestone to its estuary on the west coast of Westeros near the Shield Islands. It flows past Bitterbridge, Cider Hall, Long Table and Highgarden. It is crossed by the Roseroad at Bitterbridge and Highgarden. It is joined by the Blueburn near Long Table and by the Cockleswhent near Cider Hall.

In the books
In the Song of Ice and Fire novels Mander is the same. It was targeted by Ironborn raiders until the King of the Reach armed the shield islands two thousand years before the events of the series.