Samaras arrived at Celtic on a loan deal in January 2008 from Manchester City before making the transfer permanent after helping Celtic claim the title on the last day of the season three years ago.
He has scored 42 goals in 136 appearances for Celtic, and has been in fine form since scoring twice for the Glasgow side in their 2-0 win over city rivals Rangers at Ibrox in the New Year derby.
Ceitc manager Neil Lennon (pictured right with Samaras) described him as "unplayable" after his performance against Rangers.
Samaras said he never had any intention of moving elsewhere. "I never wanted to leave," said Samaras. "I don't care about other clubs, and I gave the manager my word I wouldn't sign a pre-contract (with another club).
"I was focused on how to get a deal with Celtic. I want to stay at this club and I am really happy about the deal.
"I have been four years at the club, and the support I have from the people inside and outside the club is magnificent.
"It is a big club who tries to win every game and win trophies, and that is the reason I signed for another three years.
"I had some conversations with the club and took our time to make the right decision."
With captain Scott Brown suspended, Samaras, 26, captained Celtic in their 2-1 win at Inverness in the Scottish Cup quarter-final on Wednesday.
"Georgios has come up for us in big games at Ibrox twice this season," said assistant manager Alan Thompson.
"He going to be a massive player for us in the future."