Waratahs coach Daryl Gibson made the announcement on Wednesday, just over a month before their round-one match against Queensland in Sydney.
Hooper captained the `Tahs to the 2014 Super Rugby title after fellow forward Dennis suffered a season-ending knee injury and the 24-year-old flanker also skippered Australia in three Tests against France that same year.
Gibson said Hooper's natural leadership got him the gig.
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"This is an opportunity for Michael to establish himself as leader of a new group with a view to the long-term future," said Gibson.
"We are extremely fortunate to have an experienced senior group behind them too, with guidance from players like Dave Dennis and Dean Mumm to assist in leading our team."
