NJ is the U.S. postal code for the state of New Jersey.
Nj or NJ may also stand for:
Places Narva-Jõesuu, Estonia Nanjing, Jiangsu, China
Science and technology Nanojoule (nJ), an International System of Units (SI) unit of energy equal to 10−9 joules Neighbor joining, a bioinformatic method for the construction of phylogenetic trees
Other uses Nj (digraph), a Latin-script digraph Nippon Jamboree Nordjyske Jernbaner, a Danish railway Napierville Junction Railway NewJeans, a South Korean girl group NJ.com, a news website
See also Nje, a letter of the Cyrillic script