Middle Mill Historic District is a national historic district located at New York Mills in Oneida County, New York. The district includes 31 contributing structures and one contributing site. It consists of a grouping of structures clustered in the vicinity of a large mill complex known as Mill Number 2 or the Middle Mills. In addition to the mill complex, there are two churches, rows of factory workers' housing, and a commercial block. It was listed on the National Register of Historic Places in 1976.