The Gunners meet top four rivals Manchester United today.
Monreal told Sky Sports: "We don't know in what position we will finish, but our target for the season is to finish in the top four. It is the target for the club and we are going to fight for that.
"We have two different ways - first is finishing fourth in the league, this is our idea and, if not, we will have the opportunity to win the Europa League and play in the Champions League next season. We have two different ways but I hope we finish in the top four and we get our target.
"The club is improving a lot. We have been working well in the last few years but probably the last two, we went down a bit and we didn't qualify for the Champions League - this was our target, honestly.
"We want to get back to playing in the Champions League next season, that's what we are waiting and fighting for and we have the opportunity."