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 |
| 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 | " Annie's Song" | James Galway |
| 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 |
| 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 |
| 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 |
- 17 Number Ones
- Most weeks at No. 1 (artist): John Travolta (14), Olivia Newton-John (14)
- Most weeks at No. 1 (song): "You're The One That I Want" - John Travolta and Olivia Newton-John (9)
- Most No.1s: John Travolta (3), Olivia Newton-John (3)
- 4 songs from the film Grease reached No. 1: "You're The One That I Want", "Summer Nights", "Sandy" and "Hopelessly Devoted to You"