Earlier this week, a consortium led by Stewart Donald successfully completed a takeover of Sunderland, and Donald acknowledged that the club needed to act swiftly regarding a replacement for Chris Coleman.
Reports emerged that Ross was in discussions with the Black Cats' hierarchy, and the League One outfit have now revealed that a two-year contract has been penned by the 41-year-old.
Ross told the club's official website: "This is a fantastic opportunity to take charge of an incredible football club. If you look the history, the facilities and most important of all, the fanbase, you can see what this club can be. To be part of the team to help realise that potential is something that fills me with excitement.
"From the moment I spoke to Stewart and Charlie, their energy and enthusiasm was evident and I share in that. There's a lot of work to be done in re-shaping the squad to ensure that we hit the ground running in League One, and I can't wait to get started."
Ross has just guided St Mirren to the Scottish Championship title.