"It really is a tremendous honour to sign for a club of Celtic's stature." said the Dutchman.
"I am really looking forward to playing for a team that has such an incredible history - and such well-known and passionate supporters."
Loovens opted for Celtic over Rangers after the Ibrox side were dumped out of Europe. With Celtic he'll get Champions League football.
"I was surprised with his decision," said Dave Jones. "That's the best way of putting it. Glenn is looking at it as the Champions League but I'm surprised he's gone to go at playing in the Scottish division.
"For me there's really only two teams up there in honesty. It's his decision and sadly his head has been turned by Celtic and Rangers. Once Rangers were out of the Champions League he's gone to Celtic."