Mislav Orsic has signed for Saints on a two-and-a-half year contract.
The 30-year-old scored 91 goals in 216 games for the Croatian side
He helped Croatia to third place in the World Cup, playing six games and scoring the winning goal.
"Mislav is a significant addition to our squad and I'm delighted we have been able to get him in so quickly."
Jones said: "He's a serious attacking threat and I'm sure anyone who has followed his progress or watched what he did at the World Cup will see what he can do." He's here and we're excited to have him.
Orsic, who has 27 caps for Croatia, leaves Dinamo Zagreb as their leading European scorer of all time.
Orisic said that he felt very happy to be a part of Saints. It's a dream for every football player to play in the premier league and I'm here, I'm ready, I'm motivated and I hope that I can help the team achieve their goals.
I'm sure I'll enjoy my time here at the camp. It is a difficult situation for the club, but I think we need to stick together. Everyone is going to stay in the premier league.
I hope we will be happy at the end of the year because we need to work hard.
In the past 13 league games, the Saints have only won one game.