This is a list of the Irish Recorded Music Association's Irish Singles Chart Top 50 number-ones of 2005.
| Issue Date | Song | Artist |
|---|---|---|
| 6 January | "Numb/Encore" | Linkin Park and Jay-Z |
| 13 January | ||
| 20 January | ||
| 27 January | ||
| 3 February | "Poison/I Believe" | Zoo |
| 10 February | "Almost Here" | Brian McFadden and Delta Goodrem |
| 17 February | "Get Right" | Jennifer Lopez |
| 24 February | "Over and Over" | Nelly featuring Tim McGraw |
| 3 March | ||
| 10 March | ||
| 17 March | "All About You/You've Got a Friend" | McFly |
| 24 March | ||
| 31 March | "(Is This the Way to) Amarillo" | Tony Christie featuring Peter Kay |
| 7 April | ||
| 14 April | ||
| 21 April | ||
| 28 April | ||
| 5 May | "Lonely" | Akon |
| 12 May | ||
| 19 May | ||
| 26 May | ||
| 2 June | "Axel F" | Crazy Frog |
| 9 June | ||
| 16 June | ||
| 23 June | ||
| 30 June | "Ghetto Gospel" | 2Pac |
| 7 July | ||
| 9 July | ||
| 14 July | ||
| 21 July | "You're Beautiful" | James Blunt |
| 28 July | ||
| 4 August | ||
| 11 August | ||
| 18 August | "Bad Day" | Daniel Powter |
| 25 August | ||
| 1 September | ||
| 8 September | ||
| 15 September | "Don't Cha" | Pussycat Dolls |
| 22 September | ||
| 29 September | ||
| 6 October | "Push the Button" | Sugababes |
| 13 October | ||
| 20 October | ||
| 27 October | "You Raise Me Up" | Westlife |
| 3 November | ||
| 10 November | ||
| 17 November | ||
| 24 November | ||
| 1 December | ||
| 8 December | "My Humps" | The Black Eyed Peas |
| 15 December | "JCB Song" | Nizlopi |
| 22 December | "Leave Right Now" | Mario Rosenstock |
| 29 December | "JCB Song" | Nizlopi |