The Welsh international had been linked with a move to the Premiership as his existing contract was due to expire in the summer. However, the 29-year-old has decided to stay for at least two more years, giving his side the perfect boost before their Scottish Cup meeting with Rangers FC on Sunday.
Hartson joined Celtic in August 2001 from Coventry City FC and has become a firm favourite with fans. The former Luton Town FC, Arsenal FC, West Ham United FC and Wimbledon FC player has scored 77 goals in 139 appearances for Celtic, and is approaching 50 caps for his country.
"I always wanted to stay and I made that clear to the manager on a number of occasions," said Hartson. "It was just a matter of sorting out a few of the finer details. I have enjoyed the success I have had in the previous three-and-a-half years."
Meanwhile, Celtic will listen to offers for utility player Mohamed Sylla. The 27-year-old has failed to command a regular place since arriving from St Johnstone FC in 2001 and is said to be seeking first-team football elsewhere.
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