Howlett, 34, has been forced to quit because of a shoulder injury suffered earlier this season.
Howlett, Munster's squad captain this term, underwent surgery in an attempt to rectify the problem but he has now decided to act on medical advice and retire.
The former Auckland wing scored a record 49 tries for New Zealand in 62 Tests.
He joined Munster in early 2008, helping them secure the Heineken Cup that season, and went on to make more than 100 appearances, scoring 35 tries.
Munster said on their official website that Howlett has intimated he will remain in Cork, where he lives with his wife and three children, for the immediate future.
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