The Saints have been woeful in the Premier League this season and just one win since November has left them hovering one point above the relegation zone with eight games remaining this term.
The final straw for the club's board came on Saturday when Southampton crashed to a 3-0 loss away to Newcastle, with a meeting called in the aftermath of the defeat to decide the best way forward.
The St Mary's Stadium outfit have since confirmed they have parted ways with Pellegrino.
“Southampton Football Club can today confirm that it has parted company with First Team Manager Mauricio Pellegrino,” said a statement, as reported by The Telegraph.
“Assistant Manager Carlos Compagnucci and Assistant First Team Coach Xavier Tamarit have also parted company with the club.
“We would like to place on record our thanks to Mauricio, Carlos and Xavier for their efforts during their time with Southampton, and wish them well for the future.
“The club will look to appoint a new management team as soon as possible, with the search for a replacement already underway.”