The 26-year old Germany international has signed a reported four-year deal for an unconfirmed fee of around £9million from Werder Bremen and Wenger was absolutely delighted to confirm the signing.
"We are delighted to welcome Per Mertesacker to the Club," Wenger told the club's official website.
"He is a German international with vast experience and strength and is good on the floor and in the air. I believe he will be well-suited to the Premier League and a tremendous asset to the team."
While Mertesacker added: "I had a great time at SV Werder Bremen and I'm grateful to the club. Moving to London enables me to fulfil a dream and a further step in my career. The Premier League has always represented a great challenge for me."