Marians has scored 39 times for the club in 106 league games, including some very important ones which have helped keep the team form struggling near the bottom.
At the announcement Marians said: "I am really pleased to have signed a new contract with Southampton. I am very happy at the club and very settled in the city.
"The fans have made me and my family very welcome and I am very happy to be staying with Saints. I really believe we can have a good season.
"I would not have signed a new contract if I did not believe this club had the potential to do well but with the new stadium and the players we have then I feel we can build on what we achieved last season.
"It was a bit wavy last season - we were up and down. Now we have to try to be more consistent because we know that on our day we can beat anyone in the league.
"Under Gordon Strachan we are fitter than ever and if we can get off to a good start then we can get into Europe, I am sure of that."
Chairman Rupert Lowe added: "Marian is a key member of our squad and I am delighted that he has extended his contract. It is another sign of the progress we are making that he is prepared to commit himself.
"We are quietly optimistic for the new season and hoping to build on two solid seasons by pushing on into the top half of the table. We are still looking to bring in new faces but we have to get the right ones," Lowe told the club's website.