| Election Name: | 2004 Washington State Senate election |
| Country: | Washington |
| Type: | legislative |
| Ongoing: | no |
| Previous Election: | 2002 Washington State Senate election |
| Previous Year: | 2002 |
| Next Election: | 2006 Washington State Senate election |
| Next Year: | 2006 |
| Seats For Election: | 28 seats of the Washington State Senate |
| Majority Seats: | 25 |
| Election Date: | November 2, 2004 |
| Image1: | Lisa Brown (cropped 1).jpg |
| Leader1: | Lisa Brown |
| Party1: | Democratic |
| Leaders Seat1: | 3rd-Spokane |
| Last Election1: | 24 |
| Seat Change1: | 2 |
| Seats After1: | 26 |
| Leader2: | Bill Finkbeiner |
| Party2: | Republican |
| Leaders Seat2: | 45th-Carnation |
| Last Election2: | 25 |
| Seat Change2: | 2 |
| Seats After2: | 23 |
| Map Size: | 350px |
| President pro tempore | |
| Before Election: | Vacant |
| After Election: | Rosa Franklin |
| After Party: | Democratic |
The 2004 Washington State Senate election was held on November 2, 2004, in which about half of the state's 49 legislative districts choose a state senator for a four-year term to the Washington State Senate.[1] The other half of state senators are chosen in the next biennial election, so that about half of the senators, along with all the members of the Washington State House of Representatives, are elected every two years.
Twenty-four seats were up for their regular election this cycle, while four seats held special elections due to resignations by their incumbents, for a total of 28 seats on the ballot. Republicans held 15 of the seats and Democrats held the remaining 13. Democrats successfully flipped two seats in the general election.[2]
The 2004 election utilized an open primary system. Primary results can be found here[3] and general election results can be found here.