Kozloduy (Bulgarian: Козлодуй pronounced [kozɫoˈduj]) is a town in northwest Bulgaria, located in Vratsa Province, on the Danube River.

The city is also known for the ship Radetzky, the boat in which the poet and revolutionary Hristo Botev and with 200 others crossed the Danube River in a final attempt to gather an army and liberate Bulgaria from the Ottoman Empire.

[citation needed] Later the Roman fort of Regianum (at Magura piatra) was built here on the Danubian Limes frontier system along the Danube.

In this region are three historic trenches which were later called Lomski, Ostrovski and Kozloduiski where a military garrison of Khan Asparukh was placed.

Bulgarians make up the largest ethnic group, followed by residents of Turkish, Roma, Russian and Romanian background.