The 29 year old said: "The last two seasons haven't been easy for me because of injuries but I feel it speaks volumes about the club's belief in me for this to be signed, and I truly believe I have a lot left to offer the club, my team-mates and all the supporters.
"It's felt like home since I arrived here four years ago and I believe we're on the verge of achieving something special together.
"I'm looking forward to the coming months and hope that together, we are all celebrating at the end of the season."
Boss Arsene Wenger said: "I have spoken many times of Tomas' class and contribution, not only on the pitch but off it as well, and I very much feel that this new contract reflects that.
"Tomas' vision and touch is remarkable and I know that we will all benefit from his input in the coming seasons. Tomas is a special talent and we're delighted that he has committed his future to Arsenal."