| Competition: | League of Ireland Premier Division |
| Season: | 1985–86 |
| Relegated: | Shelbourne UCD |
| Continentalcup1: | European Cup |
| Continentalcup1 Qualifiers: | Shamrock Rovers |
| Continentalcup2: | UEFA Cup |
| Continentalcup2 Qualifiers: | Galway United |
| Continentalcup3: | UEFA Cup Winners' Cup |
| League Topscorer: | Tommy Gaynor |
| Prevseason: | 1984–85 |
| Nextseason: | 1986–87 |
The 1985–86 League of Ireland Premier Division was the first season of the League of Ireland Premier Division. The Premier Division was made up of 12 teams.
The Premier Division was contested by 12 teams and Shamrock Rovers F.C. won the championship. The top 12 teams from the 1984–85 League of Ireland automatically qualified for the Premier Division. [2] [3]
| Team | Hometown/Suburb | Stadium | Manager | |
|---|---|---|---|---|
| Athlone Town | Athlone | St Mel's Park |  Con Flanagan | |
| Bohemians | Phibsborough | Dalymount Park | Billy Young | |
| Cork City | Cork | Turners Cross | Noel O'Mahony | |
| Dundalk | Dundalk | Oriel Park | Turlough O'Connor | |
| Galway United | Galway | Terryland Park | Tony Mannion | |
| Home Farm | Drumcondra, Dublin | Tolka Park | Mick Lawlor | |
| Limerick City | Limerick | Jackman Park | Joe O'Mahoney | |
| Shamrock Rovers | Milltown, Dublin | Glenmalure Park | Jim McLaughlin | |
| Shelbourne | Harold's Cross | Harold's Cross Stadium | Paddy Mulligan | |
| St Patrick's Athletic | Inchicore | Richmond Park | Jimmy Jackson | |
| Waterford United | Waterford | Kilcohan Park | Alfie Hale | |
| University College Dublin | Belfield | UCD Bowl |
After winning the league title in the previous season, Shamrock Rovers received automatic qualification into the first round of the European Cup. Shamrock Rovers were drawn against Hungarian club, Budapest Honvéd, 1984-85 Hungarian League Winners. Budapest Honvéd were the hosts for the first leg and won the game comfortably in a 2-0 defeat of Shamrock Rovers. In the return leg, Shamrock Rovers were defeated once again 3-1, thus eliminating them from the competition.
Budapest Honvéd won 5–1 on aggregate.
FAI Cup Runners-up, Galway United entered the European Cup Winners' Cup in the first round against Danish side, Lyngby BK. Galway United were defeated 1-0 in the away leg in Lyngby BK. In the second leg, United were defeated 3-2 at Terryland Park, ending their European campaign.