"I am delighted to have signed for Arsenal," Santos said. "It was one of my dreams to play for a major European football club and I have accomplished this.
"I am very happy to be part of this team," he said. "All the Brazilians who came to this club spoke wonders about it and I am delighted to be part of the Arsenal family."
Arsenal had been connected with the left back following an embarrassing 8-2 defeat at the hands of Manchester United, with speculation heating up over the past few days. It seemed only a matter of time before the signing went official.
The 28-year-old adds experience to a youthful back line. Manager Arsene Wenger continues to look to bolster his defense, with a further deal for German international Per Mertesacker said to be in the cards.
Wenger has gone on record saying, “Santos is a quality player, with the ability to both defend well and get forward and help with attacks.
"He has experience in the Champions League and for Brazil and has proven he can deliver at the highest level. We welcome Santos to the club and look forward to him having a big impact for us.”
Santos will get his first shot at action against Swansea when league play resumes. The club has confirmed that the player will claim the No. 11 shirt, with "A. Santos" printed on the back.