The following is a list of the IRMA's number-one singles of 2004.
| Issue date | Song | Artist |
|---|---|---|
| 1 January | "Leave Right Now" | Will Young |
| 8 January | ||
| 15 January | ||
| 22 January | ||
| 29 January | "Milkshake" | Kelis |
| 5 February | ||
| 12 February | ||
| 19 February | ||
| 26 February | ||
| 4 March | "Toxic" | Britney Spears |
| 11 March | ||
| 18 March | ||
| 25 March | ||
| 1 April | "Yeah!" | Usher featuring Lil Jon & Ludacris |
| 8 April | ||
| 15 April | "Fuck It (I Don't Want You Back)" | Eamon |
| 22 April | ||
| 29 April | "If My World Stopped Turning" | Chris Doran |
| 6 May | ||
| 13 May | "Fuck It (I Don't Want You Back)" | Eamon |
| 20 May | "The Langer" | Tim O'Riordan and Natural Gas |
| 27 May | ||
| 3 June | ||
| 10 June | ||
| 17 June | "Everytime" | Britney Spears |
| 24 June | ||
| 1 July | ||
| 8 July | ||
| 15 July | ||
| 22 July | "Dry Your Eyes" | The Streets |
| 29 July | ||
| 5 August | ||
| 12 August | "Dragostea Din Tei" | O-Zone |
| 19 August | "These Words" | Natasha Bedingfield |
| 26 August | ||
| 2 September | ||
| 9 September | "Real to Me" | Brian McFadden |
| 16 September | ||
| 23 September | ||
| 30 September | ||
| 7 October | "Call on Me" | Eric Prydz |
| 14 October | ||
| 21 October | ||
| 28 October | ||
| 4 November | "My Prerogative" | Britney Spears |
| 11 November | "Vertigo" | U2 |
| 18 November | "Lose My Breath" | Destiny's Child |
| 25 November | ||
| 2 December | "Do They Know It's Christmas?" | Band Aid 20 |
| 9 December | ||
| 16 December | ||
| 23 December | ||
| 30 December | ||