Tongan born, Fia and his family moved to New Zealand 14 years ago and he was capped by the Baby Blacks, helping them to the 2009 Junior World Championship title.
Now 25, he has gone on to establish himself as a Super Rugby regular with the Highlanders since making his debut in 2012, while he also helped Manawatu to Championship success last year, all of which means Millward is delighted to finally get his hands on Fia.
"The signing of Ma'afu is a significant one for us," Millward told the club's official website. "He's someone we targeted quite some time ago, and we would have hoped to confirm this signing much earlier in the year, only for him to pick up a ligament injury early into the Super Rugby season.
"We've monitored his recovery and are happy that he will make a big impact in an Ospreys jersey.
"He is a quality young tight-head with considerable experience who brings physicality to our front row, helping to create the strength in depth we need to be competitive all season long.
"Rugby is an attritional sport, and the front row is one of the most attritional areas of the lot, so it's important we have options available to us.
"With international call-ups and the inevitable injuries, experience shows us that we can use ten or more props across a season, so Ma'afu's presence will give us a considerable boost and we look forward to welcoming him to the Liberty Stadium."
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