That was the message from former Hoops hero Didier Agathe today as he looked ahead to his old club's forthcoming campaign.
Despite costing Celtic a bargain basement £35,000, flying full-back Agathe enjoyed some memorable moments in continental competition.
He was an important member of Martin O'Neill's team during the unforgettable run to the Uefa Cup final in Seville back in 2003.
And the defender is still remembered fondly at Parkhead for his displays against Barcelona in the same competition the following year.
The Reunion Islander gave Brazilian winger Ronaldinho – arguably the best player in the world at that point – a torrid time.
And Celts stunned their Spanish rivals by winning 1-0 at home and then drawing 0-0 away in the Nou Camp to go through to the quarter-finals.
Agathe, now running a soccer school for promising kids in his homeland, reckons the Glasgow giants belong in Europe's premier club competition. And he thinks Scott Brown, Kris Commons and Anthony Stokes should make returning to that stage for the first time since 2009 their top priority in the months ahead.
"Celtic is such a big club," he said. "They HAVE to be in the Champions League. It should be everyone's aim to get back there this season.
"I had so many memorable times in that competition. In my first season at Celtic we played, and beat, Porto, Rosenborg and Juventus.
"We also did well at home against Bayern Munich, Lyon and Anderlecht the season after we reached the Uefa Cup final."
He went on: "We played some big clubs, some of the biggest clubs in Europe – in the whole world in fact. But we always did well against them, gave a good account of ourselves.
"Okay, we had some great players at that time, the likes of John Hartson, Henrik Larsson, Stilian Petrov and Chris Sutton, and Martin O'Neill was our manager.
"But we always had 55,000 fans screaming us on at Parkhead. It could be crazy! The Celtic support is as big and as passionate as any in the world.
"Celtic has supporters all over the world, Scottish people who follow them in every country, and they should always be playing in the Champions League."
Agathe still follows the fortunes of his former club and was delighted to see them win their first Scottish title in four years last season under his old team-mate Neil Lennon.
The 36-year-old believes the next step for Celtic and Lennon is to make it from the notoriously difficult qualifying rounds into the lucrative group stage. He helped the Hoops do just that back in 2001 – by recording a stunning away victory over Dutch opponents Ajax. Goals from Agathe, Bobby Petta and Chris Sutton in the Netherlands gave O'Neill's men a famous 3-1 triumph and they duly went through.
He said: "Winning the Treble in my first season at Celtic was very special for me. I had started the season with Hibs and didn't even think I would be a player at such a club.
"But it just got better the following season when I scored in a win over Ajax and we went into the Champions League.
"The good thing for the club is that, even though many of the players have not been involved at that level, Neil Lennon and his assistant Johan Mjallby know what it is all about.
"The players have done well to win the league and I am sure they now want to go out and play in the Champions League. It is the stage that Celtic should be playing on."