The 2003 New Jersey Senate election was held on November 4.
The election took midway through Jim McGreevey's term as Governor of New Jersey. The election ended two years of split control in favor of the Democratic Party, which regained a majority for the first time since 1991. Incumbent Senate co-president John O. Bennett was unseated for re-election by Ellen Karcher in the 12th district, and Democrats also flipped a seat in the 4th.
The Democrats continue to hold the majority in the Senate as of .
Additionally, Senators John J. Matheussen, Richard Bagger, and Garry Furnari, who were elected in 2001, resigned before their terms were completed. The interim appointees for each of their seats ran as incumbents.