| 30 Aug 18 | J. Flannigan Jake Flannigan |  SouthamptonSOU | → |  Burton AlbionBRT | Loan |
| 30 Aug 18 | S. McQueen Sam McQueen | SouthamptonSOU | → |  MiddlesbroughMID | Loan |
| 30 Aug 18 | S. McQueen Sam McQueen | SouthamptonSOU | → | MiddlesbroughMID | Loan |
| 30 Aug 18 | J. Hesketh Jake Hesketh | SouthamptonSOU | → | Burton AlbionBRT | Loan |
| 27 Aug 18 | H. Reed Harrison Reed | SouthamptonSOU | → |  Blackburn RoversBLK | Loan |
| 27 Aug 18 | H. Reed Harrison Reed | SouthamptonSOU | → | Blackburn RoversBLK | Loan |
| 20 Aug 18 | J. Sims Josh Sims | SouthamptonSOU | → |  ReadingREA | Loan |
| 20 Aug 18 | J. Sims Josh Sims | SouthamptonSOU | → | ReadingREA | Loan |
| 09 Aug 18 | D. Ings Danny Ings |  LiverpoolLIV | → | SouthamptonSOU | Loan |
| 25 Jul 18 | J. Clasie Jordy Clasie | SouthamptonSOU | → |  Feyenoord RotterdamFEY | Loan |
| 25 Jul 18 | J. Clasie Jordy Clasie | SouthamptonSOU | → | Feyenoord RotterdamFEY | Loan |
| 20 Jul 18 | S. Boufal Sofiane Boufal | SouthamptonSOU | → |  Celta VigoCEL | Loan |
| 20 Jul 18 | S. Boufal Sofiane Boufal | SouthamptonSOU | → | Celta VigoCEL | Loan |
| 13 Jul 18 | J. Vestergaard Jannik Vestergaard |  Borussia MonchengladbachMON | → | SouthamptonSOU | Undisclosed |
| 13 Jul 18 | J. Vestergaard Jannik Vestergaard | Borussia MonchengladbachMON | → | SouthamptonSOU | Undisclosed |
| 10 Jul 18 | Angus Gunn |  Manchester CityMNC | → | SouthamptonSOU | Undisclosed |
| 08 Jul 18 | G. Carrillo Guido Carrillo | SouthamptonSOU | → |  LeganésLEG | Loan |
| 08 Jul 18 | G. Carrillo Guido Carrillo | SouthamptonSOU | → | LeganésLEG | Loan |
| 01 Jul 18 | D. Tadic Dusan Tadic | SouthamptonSOU | → |  Ajax AmsterdamAJA | 10000000 |
| 01 Jul 18 | D. Tadic Dusan Tadic | SouthamptonSOU | → | Ajax AmsterdamAJA | 10000000 |
| 29 Jun 18 | M. Elyounoussi Mohammed Elyounoussi |  FC BaselBAS | → | SouthamptonSOU | Undisclosed |
| 26 Jun 18 | S. Armstrong Stuart Armstrong |  CelticCEL | → | SouthamptonSOU | Undisclosed |
| 26 Jun 18 | S. Armstrong Stuart Armstrong | CelticCEL | → | SouthamptonSOU | Undisclosed |
| 26 Jan 18 | R. Seager Ryan Seager | SouthamptonSOU | → |  Yeovil TownYEO | Loan |
| 25 Jan 18 | G. Carrillo Guido Carrillo |  AS MonacoMON | → | SouthamptonSOU | Undisclosed |
| 25 Jan 18 | G. Carrillo Guido Carrillo | AS MonacoMON | → | SouthamptonSOU | Undisclosed |
| 22 Jan 18 | M. Targett Matt Targett | SouthamptonSOU | → |  FulhamFUL | Loan |
| 22 Jan 18 | M. Targett Matt Targett | SouthamptonSOU | → | FulhamFUL | Loan |
| 05 Jan 18 | M. Barnes Marcus Barnes | SouthamptonSOU | → | Yeovil TownYEO | Loan |
| 01 Jan 18 | V. van Dijk Virgil van Dijk | SouthamptonSOU | → | LiverpoolLIV | Undisclosed |