Osvaldo today agreed terms on a four-year contract with Saints and moves from Serie A side A.S. Roma.
The 27-year-old arrives with an impressive goalscoring record, with 79 goals in the 232 senior appearances he has made during his spells in Argentina, Italy and Spain.
Buenos Aires-born Osvaldo has played for Italy nine times – most recently in their friendly against his birth country last Wednesday – and has scored three goals for the Azzuri in qualifying matches for the 2014 FIFA World Cup.
He will now be reunited with Saints' First Team Manager Mauricio Pochettino, who he played under during his successful 18-month spell with Spanish side RCD Espanyol.
The frontman is expected to be available for next Saturday's Barclays Premier League game against Sunderland at St Mary's, and will be officially presented as a Southampton player tomorrow.
In Profile – Pablo Daniel Osvaldo
Pablo Daniel Osvaldo was born in the Argentinian capital of Buenos Aires on 12th January 1986.
Aged nine, he started his footballing career in the suburbs of his home city with Club Atlético Lanús, spending four years with them before moving on to nearby Club Atlético Banfield for a year.
In 2000, at the age of 14, he switched to another Buenos Aires-based side, Club Atlético Huracán. It was there that Daniel would eventually make his senior debut at the age of 19.
In his first year as a professional, Osvaldo scored 11 goals in 33 games for the the second-tier side to draw admiration from European sides.
In January 2006, the striker moved to Italian Serie B club Atalanta, playing three games towards the end of the 2005/06 season, scoring once.
That summer, Atalanta agreed a co-ownership deal for Osvaldo with fellow second-tier side Lecce, where he would move for the 2006/07 campaign.
He scored eight goals in 31 appearances during his year with the Giallorossi, leading Atalanta to recover his ownership in order to sell him onto top-flight Fiorentina.
Coincidentally, during his time with La Viola, Osvaldo played alongside Papa Waigo – who would later join Southampton on a season-long loan in 2009 – while current Saint Guly do Prado was also at the club, though the pair never appeared in a competitive game together.
By then aged 21, Osvaldo scored a brace in a 3-0 win away at Livorna on his Fiorentina debut, the first and second of six goals he would net in his first season with his new club, during which he made a total of 25 appearances in his first season with Fiorentina – including eight in the UEFA Cup.
Despite being born in Argentina, Osvaldo qualified to play for Italy by virtue of having a great-grandfather born in the country. As a result, he was called into the Under-21 squad by Pierluigi Casiraghi, making his debut in a 5-0 win over Azerbaijan on 16th November 2007.
He would go on to score his first international goal in the Under-21s' friendly win over Holland the following February, earning himself a place in the Under-23 squad that was preparing for that summer's Olympic Games football tournament.
In May 2008, Osvaldo was selected by his adopted country for the Toulon Tournament, where he would score the winning goal as the Azzuri beat their Chilean counterparts in the final.
Despite his success on the international stage, Daniel played a bit-part role at the start of the following campaign, leading him to join fellow Serie A side Bologna on loan on 20th January 2009, with a permanent transfer agreed for the following summer.
Osvaldo kicked off the 2009/10 campaign by scoring against former side Fiorentina but would find himself on the move again midway through the season, when he would be begin the most successful spell of his career to date.
On 11th January 2010, the striker signed for Spanish club RCD Espanyol, who were coached by former Argentina international and future Southampton manager Mauricio Pochettino.
Having made his debut as a substitute in Espanyol's 2-0 loss away at Osasuna, Osvaldo started their following game, scored his first goal for his new club in a 1-1 draw with RCD Mallorca on 24th January.
He would make a total of 17 starts and three substitutes during his first half-season in La Liga, netting a total of nine goals as Espanyol finished the 2009/10 campaign in 11th place.
Daniel, then 24, moved to the Estadi Cornellà-El Prat permanently that summer, with his first full season in Spain proving to be his most goal-filled to date.
The Italian scored 14 goals in 26 games as Espanyol spent the majority of the season in the top six before falling away slightly in the final month of the season to end a successful year in eighth.
His goalscoring feats for the Blanquiblaus attracted interest from Italy and, on 25th August 2011, he moved to Roma for fee in the region of €17.5million.
Handed the number nine shirt, Osvaldo went straight into the Giallorossi's side for their season-opener at home to Cagliari on 11th September.
He scored his maiden goal for the club in a 1-1 draw with Siena later that month, the first of four consecutive matches he found the net in.
As a result of his good start to life in Rome, Osvaldo was called up to the full Italy squad on 5th October 2011. He made his debut as a substitute in a 3-0 win over Northern Ireland six days later, coming up against future Saints teammate Steven Davis.
He would make his full debut for the Azzuri the following month, playing the first 65 minutes of a 1-0 friendly defeat to Uruguay at his home ground, the Stadio Olimpico in Rome.
Daniel ended the 2011/12 domestic campaign as Roma's top goalscorer with 11 from 26 appearances as his new side ended the season seventh in Serie A.
Osvaldo started last season in good form, netting in an opening-day draw with Catania and a 3-1 win away at Internazionale a week later, earning him another call-up to his national team for their 2014 FIFA World Cup qualifying games against Bulgaria and Malta.
He scored his first senior international goals in that game against Bulgaria, scoring twice in two first-half minutes as Italy drew 2-2 in Sofia.
Daniel's third goal for his country would arrive a month later, when he netted in a 3-1 qualifying win over Armenia in Yerevan to move the Azzuri closer to a place at next summer's World Cup finals.
He continued to score goals for Roma as the season went on, registering his first Serie A hat-trick in a 4-0 home win over Siena in April of this year.
Osvaldo finished the 2012/13 season as Roma's top scorer once again, with 17 goals from 31 appearances in all competitions as his side ended the campaign in sixth spot.
Despite his successful season, the striker missed out on a place in the Italy squad for the 2013 FIFA Confederations Cup, but returned for their friendly against his birth country Argentina last week, playing the full 90 minutes as Italy were beaten 2-1 at the Stadio Olimpico.
After a total of 28 goals in 57 games for Roma, Osvaldo now moves to Southampton for the next stage of his footballing career.