Goalkeeper Vasilis Barkas has joined Celtic from AEK Athens on a four-year contract.
Barkas has made more than 100 appearances for AEK since joining from Atromitos in 2016, winning the Greek top flight in 2018.
The 26-year-old has featured 10 times for Greece.
“I’m very happy to be here, it’s a dream to come to one of the biggest teams in Europe, and I can’t wait to play for Celtic,” said Barkas.
“Winning medals and trophies is why I came here. I want to win 10-in-a-row, and I want to help us get into the Champions League.”
Neil Lennon had been pursuing a new keeper after Craig Gordon departed and Fraser Forster returned to Southampton following a loan spell.
Scotland cap Scott Bain has played for Lennon’s side during pre-season while fellow goalkeeper Ross Doohan is close to joining Ross County on loan.
Celtic are reported to have paid £4.5m for Barkas.
The defending Scottish Premiership champions, who are going for a 10th successive title, open their league campaign on Sunday at home to Hamilton Academical.