Ospina stars as Nice edge Marseille
Nice's forward Dario Cvitanich celebrates after scoring a goal during their French L1 football match against Marseille on October 18, 2013 at the Allianz Riviera stadium in Nice, southeastern France
Ospina, who played in Tuesday's 2-1 World Cup qualifying win over Paraguay in Asuncion, pulled off a string of fine saves as Nice moved into fifth place in the table, four points off the lead held by Monaco.
Marseille remain fourth, ahead of Nice on goal difference.
Another South American, Argentine striker Dario Cvitanich, grabbed the only goal of the game in the 40th minute.
A minute's applause was held before kick-off in memory of former Senegal coach and Nice player Bruno Metsu, who died of cancer earlier this week.
Marseille, defeated by bitter rivals Paris Saint-Germain last time out, had the first decent chance of the game after 15 minutes.
Florian Thauvin made a sweet, accurate connection with a left foot volley from a Jeremy Morel cross.
The ball was heading towards the corner of the goal before Ospina made a smart, diving save.
But Nice were even closer on the half-hour mark when Jeremy Pied saw his volley beat Steve Mandanda in the Marseille goal but crashed back off the post.
The home side, finding their feet on a tricky Allianz Riviera pitch, took the lead five minutes from the interval.
Mahamane Traore dispossessed Rod Fanni to feed Cvitanich.
The Argentine striker rounded Mandanda to score his sixth league goal of the season and his seventh in his last eight home appearances.
Mathieu Valbuena, Marseille's creative spark, was then booked on the stroke of half-time as his frustrations boiled over.
Midfielder Gilbert Imbula rattled the woodwork for Marseille early in the second-half as the visitors dominated possession.
They should have been level 12 minutes from time but Ospina tipped over a close-range header from Andre Pierre-Gignac, who had met Andre Ayew's cross virtually unchallenged.
Ospina was on hand again in the third minute of injury time to collect a header from the acrobatic Ayew.