Best, who will win his 90th cap when Ireland open their campaign against Wales on Feb. 7, takes over the captaincy from Paul O'Connell who retired from international rugby after last year's World Cup.
The 23-year-old McCloskey, who has made a big impact with Ulster this season and former South Africa under-20 captain Stander, who qualifies for Ireland on residency grounds, were expected to be included in the otherwise experienced squad.
While coach Joe Schmidt resisted the temptation to call up exciting Leinster centre Garry Ringrose, 20, he included club mate Josh van der Flier for the first time and fellow 22-year-old, Connacht's Ultan Dillane, a surprise inclusion at lock.
Ireland will be without the injured trio of Iain Henderson, Tommy Bowe and Peter O'Mahony for the tournament. Mike Ross, Cian Healy and Chris Henry could return from injury for the final three matches, the Irish Rugby Football Union (IRFU) said.
"As always there were a number of tight decisions, especially with a number of players not being available to play in recent weeks," Schmidt said in a statement.
"There are a few new faces but at the same time we have resisted the temptation to include some of the very promising youngsters, allowing them a bit more time to develop as well as the opportunity of further game time with their provinces."
Ireland had high hopes of reaching at least the semi-final stage of the World Cup but their tournament ended in bitter disappointment after a 43-20 quarter-final defeat by Argentina in Cardiff.
Squad:
Forwards: Rory Best (captain), Sean Cronin, James Cronin, Ultan Dillane, Tadhg Furlong, Jamie Heaslip, Rob Herring, Mike McCarthy, Jack McGrath, Marty Moore, Sean O'Brien, Tommy O'Donnell, Rhys Ruddock, Donnacha Ryan, CJ Stander, Richardt Strauss, Devin Toner, Josh van der Flier, Nathan White.
Backs: Keith Earls, Luke Fitzgerald, Robbie Henshaw, Paddy Jackson, Dave Kearney, Rob Kearney, Ian Madigan, Kieran Marmion, Luke Marshall, Stuart McCloskey, Conor Murray, Jared Payne, Eoin Reddan, Jonathan Sexton, Andrew Trimble, Simon Zebo.
(Reporting by Padraic Halpin; editing by Justin Palmer)
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