Butler is a borough in Morris County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population was 8,047, an increase of 508 (+6.7%) from the 2010 census count of 7,539, which in turn reflected an increase of 119 (+1.6%) from the 7,420 counted in the 2000 census.

Butler was incorporated as a borough by an act of the New Jersey Legislature on March 13, 1901, from portions of Pequannock Township