Commenting on Cunningham's inclusion, Ulster's caretaker coach Steve Williams said: "There is obviously a lot of competition between Bryn and Mark for the full-back position and they both bring different attributes to the game.
"But this week I feel that we need Bryn wearing the number 15 jersey. He is solid at full-back and also offers a good counter attacking option."
Former All Black centre Paul Steinmetz returns to the starting line-up with Rob Dewey named as cover on the bench.
With Roger Wilson sidelined for the next weeks with a hand injury, lock-cum-flanker Matt McCullough is moved to number 8. The former Ireland Under-21 captain played Number 8 during his school days and Williams believes he will step up to the mark.
"Matt would be comfortable playing anywhere in the back row, he has great all round footballing ability and I have no doubt in my mind that he will do a good job for Ulster tomorrow night," said the Welshman.
With McCullough named in the back row, Carlo Del Fava will partner the recalled Harrison in the second row. Harrison, who played for the Barbarians against South Africa last Saturday, has gotten the nod over Ireland 'A' international Ryan Caldwell who is named on the replacements bench.
Williams said: "Justin offers us a different option in the lineout and we certainly need his expertise against the Ospreys. They will pose a massive threat in the lineout."
Meanwhile, Ulster will play the Ospreys in the return fixture at Ravenhill on Friday, December 14 and tickets are still available for the Terrace and the Memorial Stand with less than 500 Promenade tickets left.
Tickets can be purchased online from www.UlsterRugby.com and the Ulster Rugby ticket line (tel: 028 9049 3222 (Option 2)) between 10am-12 noon or alternatively from over the Ravenhill counter.
Tickets can also be bought from various ticket outlet shops across the province, including: In Sport - Newtownards, SS Moore's - Belfast, Athletic Stores - Belfast, Eden Park - Belfast, Euro Sport - Lisburn, Shoe Fair Sports -Banbridge, Style N Sport - Ballymena, Vi-Sport - Belfast, David Gotto All Sports - Belfast, Overplay Sports - Carrickfergus, Douglas & Grahame Ltd - Belfast.
ULSTER (v Ospreys): Bryn Cunningham; Tommy Bowe, Andrew Trimble, Paul Steinmetz, Simon Danielli; Paddy Wallace, Isaac Boss; Justin Fitzpatrick, Rory Best (capt), Bryan Young, Justin Harrison, Carlo Del Fava, Neil Best, David Pollock, Matt McCullough.
Replacements: Declan Fitzpatrick, Matt Miles, Ryan Caldwell, Kieron Dawson, Kieran Campbell, Niall O'Connor, Rob Dewey.