This lists songs that hit number one on the charts in the US during 2009. If a song spent nonconsecutive weeks at number one, the number of weeks for each occurrence at the top is shown in parenthesis.
| Date | Artist - Title | Weeks at #1 |
| December 21 2008 – January 10 2009 | Beyonce - Single Ladies (Put A Ring On It) | 4 (3) |
| January 11 – 31 2009 | Lady Gaga feat. Colby O'Donis - Just Dance | 3 |
| February 1 – 14 2009 | Kelly Clarkson - My Life Would Suck Without You | 2 |
| February 15 – 21 2009 | Eminem, Dr. Dre and 50 Cent - Crack a Bottle | 1 |
| February 22 – April 4 2009 | Flo Rida - Right Round | 6 |
| April 5 – 11 2009 | Lady Gaga - Poker Face | 1 |
| April 12 – July 4 2009 | Black Eyed Peas - Boom Boom Pow | 12 |
| July 5 – October 10 2009 | Black Eyed Peas - I Gotta Feeling | 14 |
| October 11 – 17 2009 | Jay Sean feat. Lil Wayne - Down | 2 (1) |
| October 18 – 24 2009 | Britney Spears - 3 | 1 |
| October 25 – 31 2009 | Jay Sean feat. Lil Wayne - Down | 2 (1) |
| November 1 – 7 2009 | Owl City - Fireflies | 2 (1) |
| November 8 – 14 2009 | Jason DeRulo - Whatcha Say | 1 |
| November 15 – 21 2009 | Owl City - Fireflies | 2 (1) |
| November 22 – December 26 2009 | Jay-Z and Alicia Keys - Empire State of Mind | 5 |
| December 27 2009 – February 27 2010 | Ke$ha - TiK ToK | 9 |
14 different songs hit number one in the US during 2009.
Top 5 Songs of 2009
1: Black Eyed Peas - Boom Boom Pow
2: Lady Gaga - Poker Face
3: Lady Gaga - Just Dance
4: Black Eyed Peas - I Gotta Feeling
5: Taylor Swift - Love Story
2: Lady Gaga - Poker Face
3: Lady Gaga - Just Dance
4: Black Eyed Peas - I Gotta Feeling
5: Taylor Swift - Love Story