The 25-year-old, who impressed for his country at the World Cup in Brazil, has moved to the Emirates Stadium for an undisclosed fee.
Gunners manager Arsene Wenger told Arsenal's official website: "David Ospina is an excellent goalkeeper, with good experience and a proven record of performing with Nice and Colombia.
"Ospina is an excellent goalkeeper, with good experience and a proven record"
Arsene Wenger
"He will add strength to our squad and we are very pleased that he will be joining us."
The keeper is expected to make his first appearance for Arsenal during the Emirates Cup friendly tournament, which takes place in north London next weekend.
His first competitive appearance could come in The FA Community Shield next month at Wembley where the Gunners take on Premier League champions Manchester City.
Ospina made 189 Ligue 1 appearances over six years with Nice having joined the club from Colombian club Atletico Nacional in 2008.
He made his senior debut for Atletico aged just 17 and has been a full Colombia international since 2007, making his first start for Los Cafeteros in a 2010 World Cup qualification match against Bolivia.
At Arsenal he will provide competition for first-choice keeper Wojciech Szczesny while helping to fill the gap left by the departed Lukasz Fabianski, who has joined Swansea.
