Scott McDonald is well known to Celtic fans

The Fir Park club announced the deal earlier this week and the 23-year-old Australian has now completed a medical.

McDonald, who will stay with Motherwell until the end of the season, told the Celtic website: "It's a great day for the whole family.

"My dad's side of the family are all massive Celtic fans and I was brought up in Australia as a Celtic supporter."

Maurice Malpas on McDonald transfer

McDonald worked with Celtic management team Gordon Strachan and Garry Pendrey during his spell as a trainee at Southampton.

And he said: "I can't wait to work with them again.

"I'm sure they will bring my game on a lot and it will be a great challenge for me at Celtic.

"There are a lot of quality players at this club but I'm willing to fight for my place."

McDonald was disappointed to miss out on a January move to Rangers, who offered �400,000 on transfer deadline day.

But Rangers were reportedly unwilling to match Celtic's bid, believed to be �700,000.

The striker has hit 12 goals in 34 appearances for Motherwell this season, including one against Celtic in October.

But he will be best known to Celtic fans for the late double he struck against them on the final day of the 2004-05 season which handed the SPL title to Rangers.

Earlier this week, McDonald told the Fir Park club's website: "I have thoroughly enjoyed playing for Motherwell and I will leave with a lot of good memories.