Sunderland have completed the signing of striker Steven Fletcher from Wolves on a four-year deal.
The Scot joined Wolves from Burnley in 2010 for a fee of £7 million, and scored 12 goals as the Midlands club dropped out of the Premier League.
Speaking to the club's Official website, Martin O'Neill said: "It has been no secret that we needed to strengthen our attacking options and Steven has a proven track record of scoring goals.
"He is young and constantly improving and he will be a very welcome addition to the squad. I'm delighted that we've been able to bring him to Sunderland."
Fletcher, 25, has been a long-term target for the Wearsiders and was keen to remain in the Premier League having submitted a transfer request earlier in the month.
Speaking to SAFCTV Fletcher said: "I'm delighted and relieved. It's taken a while but I'm glad it's finally done. When I come to the training ground and see things like this, it obviously shows how big the clubs is.
"I went to the stadium yesterday and saw that as well. I've played here a few times, the atmosphere is always good- I'm looking forward to it.
"When he [Martin O'Neill] was at Celtic I used to watch Celtic. No one has ever said a bad thing about him, everyone praises him. When I met him for the first time, I knew this was the right thing for me. I'm looking forward to working with him.
"It's very positive, the signings he's brought in and the squad he's already got as well. I watched training yesterday and watched a bit today and the boys are looking very sharp. I'm excited. I've got family here so they told me everyday when I was speaking with them when I was linked with the club about the supporters- so I'm looking forward to playing. There Sunderland fans too which is an added bonus."
The former Hibs forward is likely to go straight into the squad ahead of Saturday's game against Reading at the Stadium Of Light.
Fletcher's transfer represents Sunderland's third signing of the summer following the arrival of Carlos Cuellar and Louis Saha from Aston Villa and Tottenham respectively.