This is a list of singles which have reached number one on the Irish Singles Chart in 1978.
| Week ending | Song | Artist | | 7 January | Mull of Kintyre | Wings |
| 14 January |
| 21 January |
| 28 January |
| 4 February |
| 11 February |
| 18 February | Figaro | Brotherhood of Man |
| 25 February | Take a Chance on Me | ABBA |
| 4 March | The Rare Auld Times | Danny Doyle {{flagicon|Ireland}} |
| 11 March |
| 18 March | Wuthering Heights | Kate Bush |
| 25 March |
| 1 April |
| 8 April | Matchstalk Men and Matchstalk Cats and Dogs | Brian and Michael |
| 15 April |
| 22 April |
| 29 April | Night Fever | The Bee Gees |
| 6 May |
| 13 May |
| 20 May | Rivers of Babylon | Boney M |
| 27 May |
| 3 June |
| 10 June |
| 17 June |
| 24 June | You're the One That I Want | John Travolta and Olivia Newton-John |
| 1 July |
| 8 July |
| 15 July |
| 22 July |
| 29 July |
| 5 August |
| 12 August |
| 19 August | Substitute | Clout |
| 26 August | You're the One That I Want | John Travolta and Olivia Newton-John |
| 2 September | Three Times a Lady | The Commodores |
| 9 September |
| 16 September |
| 23 September | Summer Night City | ABBA |
| 30 September | One Day at a Time | Gloria {{flagicon|Ireland}} |
| 7 October | Summer Nights | John Travolta and Olivia Newton-John |
| 14 October |
| 21 October |
| 28 October |
| 4 November | Sandy | John Travolta |
| 11 November | One Day at a Time | Gloria {{flagicon|Ireland}} |
| 18 November | Hopelessly Devoted to You | Olivia Newton-John |
| 25 November | Mary's Boy Child – Oh My Lord | Boney M |
| 2 December |
| 9 December |
| 16 December |
| 23 December |
| 30 December |
|