Original Under Armour Football Shirt Southampton 2018/19

The 2018–19 Southampton F.C. season was the club's 20th season in the Premier League and their 42nd in the top division of English football. In addition to the Premier League, the club also competed in the FA Cup and the EFL Cup. Southampton finished the season 16th in the Premier League table with 9 wins, 12 draws and 17 losses. The club were knocked out of the third round of the FA Cup by Championship side Derby County, and were knocked out of the EFL Cup in the fourth round by fellow Premier League team Leicester City. The 2018–19 season was Southampton's last with manager Mark Hughes, who departed on 3 December 2018 with the club in the relegation zone with only one win from fourteen games. Former RB Leipzig manager Ralph Hasenhüttl was appointed as his replacement the next day, after Kelvin Davis took charge of the team's next game.

Following the end of the 2017–18 season, Southampton released a number of players, including first-team defenders Florin Gardoș and Jérémy Pied. The club also sold Serbian midfielder Dušan Tadić to Dutch club Ajax for £10 million. Several players were also brought in during the summer – Scottish midfielder Stuart Armstrong from Premiership champions Celtic for £7 million, Norwegian winger Mohamed Elyounoussi from Swiss side Basel for £16 million, goalkeeper Angus Gunn from Premier League champions Manchester City for £13.5 million, and Danish centre-back Jannik Vestergaard from German club Borussia Mönchengladbach. In August, Liverpool striker Danny Ings joined on an initial loan, with a permanent move planned for the following summer. A number of players were loaned out, including striker Guido Carrillo, playmaker Sofiane Boufal, and midfielder Jordy Clasie.

In the January transfer window, the club sold out-of-favour striker Manolo Gabbiadini to Italian side Sampdoria for an undisclosed fee. Midfielder Steven Davis also returned to his former club Rangers on loan until the end of the season, while Wesley Hoedt and Cédric Soares moved to Celta Vigo and Inter Milan on loan until the end of the season respectively.