Hartley was dropped for the SPL game against Rangers

Rangers had failed with several bids for Hartley before the lifelong Celtic fan ended up at Gordon Strachan's club.

The 30-year-old has signed a two-and-a-half-year contract, with the option for a further year.

"I've never hidden the fact that I'm a Celtic supporter, so you can imagine what this means to me," Hartley told the Scottish Sun.

Hartley, capped six times by Scotland, will be reunited with his former Hearts team-mate, Steven Pressley, at Celtic.

He will be officially unveiled at a media conference at Celtic Park on Thursday.

Hartley, who last year signed a new contract with Hearts, was omitted from head coach Valdas Ivanauskas' side that drew with Rangers at the weekend.

Ivanauskas said Hartley was omitted due to "football business".

That was thought to have been a bid from Rangers, but it was second time lucky for Celtic after the Scottish champions failed to secure the player last January.

Hartley had two years of his contract to run.

But, in October, he appeared in public alongside goalkeeper Craig Gordon and former captain Pressley as the Scotland defender said there was "dressing-room unrest".

Pressley has since moved to Celtic, while Gordon has been surprisingly dropped from the starting line-up on a couple of occasions.