Tandy becomes the 11th player to reach a century of Ospreys caps, and coach Jonathan Humphreys has handed the veteran back-rower the armband to mark the occasion.
Humphreys said: "We have Steve Tandy making his 100th appearance for the region and captaining the team for the first time.
"One of the original Ospreys, Steve has been, and continues to be, a tremendous servant to the region, and along with the likes of Andy Lloyd and Sonny Parker will have an important part to play over the coming weeks as one of the senior players in the group."
exciting time for this group of players with the challenge of the LV= Cup followed by two important games as we look to secure a place in the end of season-play-offs. It's certainly going to be an interesting time, particularly with so many younger players coming into contention during this period looking to show what they can do and stake a claim for a place.
"Our options for this game have been enhanced by Wales allowing four players to come back to us. In the case of Shane and Adam, it is clear that they need more game time after lengthy spells on the sidelines, while the likes of Tom and Kristian were always pencilled in for involvement this weekend so we are happy to welcome them back."
Ospreys: 15 Barry Davies 14 Kristian Phillips 13 Sonny Parker 12 Ashley Beck 11 Shane Williams 10 Gareth Owen 9 Jamie Nutbrown
1 Ryan Bevington 2 Ed Shervington 3 Adam Jones 4 Andy Lloyd 5 Ian Evans 6 Ben Lewis 7 Steve Tandy (Capt) 8 Tom Smith
Replacements: 16 Marc Breeze 17 Craig Mitchell 18 Cai Griffiths 19 James Goode 20 James King 21 Rhys Webb 22 Matthew Jarvis 23 Tom Prydie