NIZHNE-UDINSK, a town of East Siberia, in the government of Irkutsk, 315 m. by rail W.N.W. of Irkutsk, on the Siberian railway, and on the Uda river. It is a centre for the Biryusa gold mines, and in winter the head of a line of communication with the Lena and Bratsky Ostrog, on the Angara. Pop. (1897) 5803.