Horgan captained Ireland 'A' to an impressive 48-19 victory over Tonga at Ravenhill last Friday.
Gordon D'Arcy comes in at centre, linking up with Ireland captain Brian O'Driscoll, and there is a new half-back partnership with Jonathan Sexton earning his first cap at number 10 and his provincial colleague Eoin Reddan starting at scrum half.
Tom Court starts the game at loosehead prop and Leo Cullen comes into the side to partner Paul O'Connell in the second row. There is one change to the back row with Denis Leamy replacing David Wallace.
The replacements include Andrew Trimble and the uncapped Sean O'Brien, both of whom were involved in the recent 'A' game against Tonga.
Tomas O'Leary, Paddy Wallace and Donncha O'Callaghan have been named amongst the replacements after starting against Australia, with Tony Buckley and the uncapped Sean Cronin completing the bench.
Commenting on the team changes, Ireland coach Declan Kidney said: "We took it about who has been training well all the time. We talk about building a squad and a lot of the guys here haven't got a go for some time.
"Shane Horgan backed it up with an extremely good start to the season. You have to show belief in your players and I think that's what we have done with who we have selected.
"I thought the Ireland 'A' guys went quite well (against Tonga), it's always difficult to judge.
"I thought they scrummaged well and obviously there are other parts of the play on top of that. Those lads are starting to come stronger.
"We have the 'A' game in Tallaght and the Test against South Africa too next weekend. We are trying to give recognition to the lads whilst also recognising the lads that are coming through."
On the injury front, Kidney added: "We've just two out. Luke Fitzgerald, whom you know about, and Cian Healy who got a bang to his shoulder. With a six-day turnaround it wasn't going to clear up in time."
IRELAND TEAM & REPLACEMENTS (v Fiji, GUINNESS Series 2009, The RDS, Saturday, November 21, kick-off 5.15 pm):
15 - Rob Kearney (UCD/Leinster)
14 - Shane Horgan (Boyne/Leinster)
13 - Brian O'Driscoll (UCD/Leinster) (capt)
12 - Gordon D'Arcy (Lansdowne/Leinster)
16 - Sean Cronin (Buccaneers/Connacht)*
17 - Tony Buckley (Shannon/Munster)
18 - Donncha O'Callaghan (Cork Constitution/Munster)
19 - Sean O'Brien (Clontarf/Leinster)*
20 - Tomas O'Leary (Dolphin/Munster)
21 - Paddy Wallace (Ballymena/Ulster)
22 - Andrew Trimble (Ballymena/Ulster)
* denotes uncapped player