Derek Riordan has signed a three-year contract with Celtic after the SPL champions agreed a fee with Hibernian to allow him to move immediately.
Riordan is excited at the prospect of playing for Celtic
The 23-year-old had been due to make the move in January after signing a pre-contract agreement, but Celtic have now paid Hibs compensation.
Celtic have the option of extending the contract by a further year.
"It's a big step for me. I hope I can get into the team, play well and score goals," Riordan said.
Celtic manager Gordon Strachan welcomed the agreement that allowed Riordan to join Celtic for pre-season training.
"It's a bonus for everyone. It's great for us and more importantly for the player," he added.
Strachan revealed that Riordan had been wary of the array of talent already at the club.
"Derek was a bit worried about the strong squad with Nakamura, Maloney and McGeady," he said.
"But I told him 'they know you're coming and they're a bit worried too'."
Strachan believes Riordan is in a similar mould to a number of his other recent signings - Kenny Miller, Gary Caldwell and Evander Sno.
"They're all younger sort of players, they can all pass, they're intelligent and that means they can get better.
"We've signed players who can adapt. With the amount of games we'll have they might need to play in different positions.
"Derek comes alive in the final third, he can make that crucial pass and he stays clinical whether he's getting a goal himself or putting another player in."
Strachan added that his involvement in the summer transfer market was unlikely to be over.
"We're still actively looking. We're looking for a bit of experience now," he added.
"You can't just have a young team - we have to merge that with a bit of experience."
Chief executive Peter Lawwell added of Riordan: "Derek is one of Scotland's most exciting young players and I am sure there were a number of other clubs keen to sign him.
"However, we are delighted to have secured his signature and announce him as our third new signing this week."