The Arsenal manager expects Giovanni Trapattoni's men to be tough to beat at the European Championships but does not see them progressing to the knockout stages
The Irish are the rank outsiders in Group C, which also contains Italy and Croatia, but, while Wenger thinks they have little chance of progressing to the knockout stages, he insisted Giovanni Trapattoni's men can have a big say in how the group pans out.
He told the Gunners' official website: "Spain are the favourites, and second favourite in this group are Italy of course. The outsider is Croatia.
"Ireland are a team that will be difficult for every opponent. First of all they have a fighting spirit, and they also have Trapattoni, who knows how to not lose games."
The Frenchman still expects Vicente del Bosque's side to top the group, leaving the Italians - who recently suffered a 3-0 defeat to Russia - and Croatia to compete for the final qualification spot.
"Overall it is a very even group," he added.
"Talent-wise you would say Spain are above the rest, after that it depends if Italy can score goals because, while they have tactical knowledge, they have a problem scoring goals.
"It will be interesting to see who comes out here, but at the start you would think Spain certainly, second it can be decided between Croatia and Italy."