McDonald had a season to remember last term, scoring a total of 31 goals to help Celtic to yet another SPL title.
Celtic Chief Executive Peter Lawwell said: "This is great news for Celtic. It is well known that Scott loves playing for Celtic and he has a great affection for the club. He is also someone who performed brilliantly for Celtic last season.
"Our priority is always to keep our best and most committed players and the Board is delighted to support Gordon in his plans for the future by securing Scott on this long-term agreement.
"We will continue to do all we can to ensure that Celtic stays at the top of Scottish football."
Amen to that Peter!
Yours in Celtic
Clydebuilt