| Competition: | Segunda División |
| Season: | 1965–66 |
| Winners: | Deportivo La Coruña Hércules |
| Promoted: | Deportivo La Coruña Hércules Granada |
| Relegated: | Hospitalet Melilla Baracaldo Badajoz |
| League Topscorer: | Abel Fernández (26 goals) |
| Best Goalkeeper: | José Antonio Fernández (0.62 goals/match) |
| Biggest Home Win: | (12 September 1965) (19 September 1965) (25 December 1965) |
| Biggest Away Win: | (2 January 1966) |
| Highest Scoring: | (5 December 1965) (25 December 1965) |
| Matches: | 480 |
| Total Goals: | 1259 |
| Prevseason: | 1964–65 |
| Nextseason: | 1966–67 |
The 1965–66 Segunda División season was the 35th since its establishment and was played between 5 September 1965 and 3 April 1966.
32 teams joined the league, including 4 relegated from the 1964–65 La Liga and 4 promoted from the 1964–65 Tercera División.
| Goalscorers | Goals | Team |
|---|---|---|
 Abel Fernández | 26 | Celta Vigo |
| 19 | Deportivo La Coruña | |
| Martí Filosia | 16 | Condal |
| Miguel Ángel Montes | 15 | Real Gijón |
| Carles Feliu | 15 | Condal |
| Goalkeeper | Goals | Matches | Average | Team | |
|---|---|---|---|---|---|
| Benito Joanet | 19 | 28 | Deportivo La Coruña | ||
| Rafael Alarcia | 22 | 30 | Oviedo | ||
| José Ramón Ibarreche | 28 | 30 | Celta Vigo | ||
| Carlos Patiño | 31 | 30 | Lérida | ||
| Lucrecio Luquin | 30 | 25 | Osasuna |
| Goalscorers | Goals | Team |
|---|---|---|
| Mendi | 18 | Atlético Ceuta |
| José Juan Gutiérrez | 15 | Tenerife |
| Juan Ramón Arana | 12 | Hércules |
| José Luis García | 10 | Valladolid |
| 10 | Valladolid | |
| Goalkeeper | Goals | Matches | Average | Team | |
|---|---|---|---|---|---|
| José Antonio Fernández | 16 | 26 | Levante | ||
| Victoriano Bilbao | 14 | 20 | Hércules | ||
| Juan Ignacio Otero | 20 | 24 | Granada | ||
| José Bermúdez | 21 | 25 | Cádiz | ||
| José Antonio Omist | 27 | 29 | Algeciras |