Subject of transfer rumours for most of the summer, Armstrong has committed his immediate future to the Scottish champions after agreeing to a one-year extension on his previous deal, which was due to expire in the summer of 2018.
The player said in a club statement: “I am delighted to sign this new contract with Celtic. I have had a tremendous time at the club so far and it has been a period in my footballing career which I have enjoyed immensely.
“It has been an honour to play for a club of such stature. I have enjoyed a great relationship with our supporters and we have achieved a high level of success, something it has been great to be part of.
“I’m pleased that this new contract has been agreed and I am now looking forward very much to working with the manager, our staff and my team-mates to bring the club and our fans even more success.”