The Middletown and New Jersey Railroad (reporting mark MNJ) is one of two railroads in the city of Middletown, New York; the other being its interchange partner, Norfolk Southern Railway. The MNJ consists of 43 miles (69 km) of track in southeastern New York serving Orange County and the Hudson Valley. The railroad also operates and has trackage rights on three additional branch lines (the Hudson Secondary, Maybrook and Walden Industrials, and Southern Tier) totalling 40 miles (64 km) leased from Norfolk Southern in Orange County. It was known as the Middletown and New Jersey Railway until 2009, when East Penn Railroad parent Regional Rail, LLC bought the line through a new subsidiary. In 2015, Regional Rail was in turn acquired by Levine Leichtman Capital Partners ("LLCP").

In 2012, the Middletown and New Jersey Railroad, LLC, received a $1.6 million New York State Department of Transportation (NYSDOT) grant to perform rail upgrades on the four lines it operates in Orange County. The railroad rehabilitated the line between Campbell Hall and Warwick and portions of the track in Middletown and between Walden and Montgomery.