Ust-Barguzin (; , Bargazhanaj Adag) is an urban locality (an urban-type settlement) in Barguzinsky District of the Republic of Buryatia, Russia, located on the shore of Lake Baikal at the mouth of the Barguzin River and northeast of Ulan-Ude, the capital of the republic. As of the 2010 Census, its population was 7,173.