The following is a list of the IRMA's number-one singles of 2003.
| Issue Date | Song | Artist |
|---|---|---|
| 4 January | Lose Yourself | Eminem |
| 11 January | Sound of the Underground | Girls Aloud |
| 18 January | ||
| 25 January | ||
| 1 February | All the Things She Said | T.A.T.u. |
| 8 February | ||
| 15 February | ||
| 22 February | ||
| 1 March | Beautiful | Christina Aguilera |
| 8 March | ||
| 15 March | ||
| 22 March | ||
| 29 March | Tonight | Westlife |
| 5 April | A Better Plan | Simon Casey |
| 12 April | ||
| 19 April | ||
| 26 April | In da Club | 50 Cent |
| 3 May | We've Got the World | Mickey Harte |
| 10 May | ||
| 17 May | ||
| 24 May | ||
| 31 May | ||
| 7 June | Ignition | R. Kelly |
| 14 June | ||
| 21 June | ||
| 28 June | May We Never Have to Say Goodbye | Ronan Tynan and Rita Connolly |
| 5 July | ||
| 12 July | Crazy in Love | Beyoncé featuring Jay-Z |
| 19 July | ||
| 26 July | ||
| 2 August | ||
| 9 August | Fly on the Wings of Love | XTM |
| 16 August | ||
| 23 August | Breathe | Blu Cantrell featuring Sean Paul |
| 30 August | ||
| 6 September | Where Is the Love? | The Black Eyed Peas |
| 13 September | ||
| 20 September | ||
| 27 September | ||
| 4 October | ||
| 11 October | ||
| 18 October | ||
| 25 October | ||
| 1 November | ||
| 8 November | Be Faithful | Fatman Scoop featuring The Crooklyn Clan |
| 15 November | Me Against the Music | Britney Spears featuring Madonna |
| 22 November | Mandy | Westlife |
| 29 November | ||
| 6 December | ||
| 13 December | Shut Up | The Black Eyed Peas |
| 20 December | Leave Right Now | Will Young |
| 27 December |
|
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