This is a list of the IRMA's Irish Singles Chart Top 50 number-ones of 2009.
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| Issue Date | Song | Artist |
|---|---|---|
| 1 January | "Hallelujah" | Alexandra Burke |
| 8 January | ||
| 15 January | "Just Dance" | Lady Gaga featuring Colby O'Donis |
| 22 January | ||
| 29 January | ||
| 5 February | ||
| 12 February | ||
| 19 February | "Get On Your Boots" | U2 |
| 26 February | "Poker Face" | Lady Gaga |
| 6 March | ||
| 13 March | "Do You Believe" | Julie-Anne Dineen |
| 20 March | "Right Round" | Flo Rida featuring Ke$ha |
| 27 March | ||
| 2 April | ||
| 9 April | "Jai Ho! (You Are My Destiny)" | A.R. Rahman & The Pussycat Dolls featuring Nicole Scherzinger |
| 16 April | ||
| 23 April | "We Made You" | Eminem |
| 30 April | "Poker Face" | Lady Gaga |
| 7 May | "Number 1" | Tinchy Stryder featuring N-Dubz |
| 14 May | ||
| 21 May | ||
| 28 May | ||
| 4 June | ||
| 11 June | "Untouched" | The Veronicas |
| 18 June | "When Love Takes Over" | David Guetta featuring Kelly Rowland |
| 25 June | "My Baby's Waiting" | Industry |
| 2 July | "When Love Takes Over" | David Guetta featuring Kelly Rowland |
| 9 July | ||
| 16 July | "I Gotta Feeling" | The Black Eyed Peas |
| 23 July | ||
| 30 July | ||
| 6 August | ||
| 13 August | ||
| 20 August | ||
| 27 August | "Burn" | Industry |
| 3 September | "I Gotta Feeling" | The Black Eyed Peas |
| 10 September | ||
| 17 September | ||
| 24 September | ||
| 1 October | ||
| 8 October | ||
| 15 October | "Bad Boys" | Alexandra Burke featuring Flo Rida |
| 22 October | "Fight for This Love" | Cheryl Cole |
| 29 October | ||
| 5 November | ||
| 12 November | ||
| 19 November | "You Are Not Alone" | The X Factor Finalists 2009 |
| 26 November | ||
| 3 December | ||
| 10 December | "Bad Romance" | Lady Gaga |
| 17 December | "The Climb" | Joe McElderry |
| 24 December | ||
| 31 December |