Wenger has opted to stick with his Colombian shot-stopper despite Petr Cech – the clubs undisputed No.1 – returning to full fitness after missing Sundays win over West Ham.
Ospina is the clubs cup goalkeeper, even though he did not play in the last round against CSKA, and Wenger has stuck by his promise to give him European football this season.
The decision to pick Ospina over Cech reportedly surprised a number of the Arsenal squad given the importance of Thursdays Europa League semi-final first-leg clash.
Winning the competition now represents Arsenals only chance of silverware this season, and only means of qualifying for the Champions League.
Wenger has, however, named his strongest possible side Ospina apart, with Mesut Ozil back in the line-up despite missing the weekend victory over West Ham.
Atletico boss Diego Simeone, meanwhile, has left former Chelsea striker Diego Costa on the bench as he works his way back from a hamstring injury.
The Spain international took part in training at the Emirates yesterday and looked sharp, but Simeone was conscious of not rushing him back too soon, with Antoine Griezmann still providing significant menace up front for the visitors.
More: Arsenal FC