The 2003 United States state legislative elections were held on November 7, 2003, alongside other elections. Elections were held for 8 legislative chambers in four states. Both chambers of the Northern Mariana Islands legislature were up.
Partisan change only occurred in one chamber, as Democrats won control of the New Jersey Senate, which was previously tied. However, Democrats did maintain control of the Mississippi Legislature, the Louisiana Legislature, and the New Jersey General Assembly. Republicans maintained control of the Virginia legislature, bringing a post-Civil War low for the Democratic Party.
Regularly scheduled elections were held in 8 of the 99 state legislative chambers in the United States. Nationwide, regularly scheduled elections were held for 578 of the 7,383 legislative seats. This table only covers regularly scheduled elections; additional special elections took place concurrently with these regularly scheduled elections.
Ratings are designated as follows:
All seats of the Louisiana State Senate and the Louisiana House of Representatives were up for election to four-year terms in single-member districts. Democrats maintained control of both chambers.
All seats of the Mississippi State Senate and the Mississippi House of Representatives were up for election to four-year terms in single-member districts. Democrats maintained control of both houses.
All seats of the New Jersey Senate and the New Jersey General Assembly were up for election. Senators were elected to two-year terms in single-member districts, while Assembly members were elected to two-year terms in two-member districts. Democrats retained control in of the lower house and won control of the upper house.
All seats of the Senate of Virginia and the Virginia House of Delegates were up for election in single-member districts. Senators were elected to four-year terms, while delegates served terms of two years. Republicans maintained control of both houses.
All seats of the Northern Mariana Islands House of Representatives and half of the Northern Mariana Islands Senate are up for election. Senators are elected to four-year terms and Representatives are elected to two-year terms.