It partially flows along the borders of Chelyabinsk and Kurgan Oblasts with Kazakhstan.

[1] It rises in the southern Ural Mountains east of the headwaters of the Ural between Chelyabinsk and Magnitogorsk and flows east with many meanders past Troitsk to meet the Tobol near Zverinogolovskoye (formerly the fort of Ust-Uysk).

At the time of the Bashkir War of 1735-40 it was the eastern end of the Orenburg Line of forts and is now approximately part of the border between Russia and Kazakhstan.

The Uy is the southernmost river on the east side of the Urals whose waters ultimately reach the Arctic Ocean.

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