Loch Eck is a freshwater loch located on the Cowal peninsula, north of Dunoon, Argyll and Bute, Scotland. It is seven miles long. Apart from Loch Lomond, it is the only naturally occurring habitat of the Powan (fish).

Loch Eck is within the Argyll Forest Park which, is itself part of the Loch Lomond and The Trossachs National Park.

The loch is also an impounding reservoir with a concrete dam measuring 0.870 metres high. The dam was completed in 1973. Loch Eck now supplies the freshwater to much of the southeast of Cowal, including Dunoon.

In July 2013, two dogs died due to algal bloom present in the loch. Warnings were then posted advising that people and animals should avoid contact with the water