Elections to the 109th United States House of Representatives were held on November 2, 2004. The House of Representatives has 435 seats; in the 108th Congress, Republicans held 227 seats, Democrats held 205, with two Republican vacancies and one independent. As a consequence of this election, the 109th United States House of Representatives is composed of 232 Republicans, 202 Democrats and one independent, Bernard Sanders of Vermont (who usually votes with the Democrats). The Republicans built up their House majority by 3 seats (gaining 7 but losing 4).
Of the seven gross seats the Republicans gained, five can be attributed to a special redistricting plan in Texas led by Republican Representative Tom DeLay. His redistricting plan was put into action, turning five Democratic seats Republican. A mid-decade redistricting like this was unprecedented and controversial.
Outside of Texas, Democrats gained two seats net, gaining open seats in Colorado and New York and ousting incumbents in Georgia and Illinois. Republicans gained an open seat in Kentucky and ousted an incumbent in Indiana. A pair of seats in Louisiana swapped party control.
On the same date occurred:
Table showing incumbents for each district by party
Voting members
Key to party abbreviations:
C=Constitution, D=Democrat, G=Green, I=Independent, IP=Independence Party, L=Libertarian, R=Republican
Alabama
Alaska
| District | Incumbent | Party | Elected | Status | Result |
| Alaska At Large | Don Young | Republican | 1973 | Running | Don Young (R) 72% Thomas Higgins (D) 22% Timothy Feller (G) 4% Alvin Anders (L) 2% |
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
On December 4, 2004, a run-off election was held to determine the winner of the 3rd and 7th Congressional districts. In the 3rd district, Charlie Melancon narrowly defeated Billy Tauzin III 50.25-49.75. In the 7th district, Charles Boustany defeated Willie Mount 55-45. Thus, both seats switched to the opposite party.
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
| District | Incumbent | Party | Elected | Status | Opponent |
| Nebraska 1 | Vacant | (Seat was Republican in 2002) | -- | -- | Jeff Fortenberry (R) 54% Matt Connealy (D) 43% Steve Larrick (G) 3% |
| Nebraska 2 | Lee Terry | Republican | 1998 | Running | Lee Terry (R) 61% Nancy Thompson (D) 36% Jack Graziano (L) 2% Dante Salvatierra (G) 1% |
| Nebraska 3 | Tom Osborne | Republican | 2000 | Running | Tom Osborne (R) 87% Donna Anderson (D) 11% Joseph Rosberg (I) 1% Roy Guisinger (G) 1% |
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania