Hinchcliffe is a member of the Storm leadership group and captained the side in their recent NRL game against Penrith, although he was on the bench for Sunday's defeat to Brisbane Broncos.
He has made a total of 184 appearances in the NRL, 163 of them since joining the Storm from Canberra in 2009, and has twice won the NRL Grand Final and played in two World Club Challenges.
Giants head coach Paul Anderson said: “This is a huge signing for our club and in truth Ryan has been our number one target to bring in for quite some time now. He is a quality nine but equally at home at loose forward.
“He has been in one of the best environments in rugby league at Melbourne for seven years now being an automatic pick in the side. His defensive efforts are up there with the best and I particularly like what he will bring with his leadership and experience in big games.
“You simply don’t get to lead the Melbourne Storm side out unless you have very special qualities and his NRL record is outstanding. We are looking forward immensely to welcoming him and his family to our club.”
Hinchcliffe said: “Huddersfield made their interest known quite some time back and I’ve had a few chats with coach Paul Anderson about the team and what he’s looking for. They’ve been close to the top for a few years and I hope that I can help them build on that.
“The reality is though it’s a big move for me and the family to a new culture and we hope we can repay Huddersfield’s faith in us.
“For now my focus is purely on finishing well here at the Melbourne Storm and then the focus will shift to the UK and Huddersfield, where I look forward to the challenges it presents."
Italy's Rugby World Cup preparations have been thrown into chaos by a player strike over tournament bonuses.
The Italian Rugby Federation (FIR) claims to have "taken note" of the players' stance, that includes demanding a match-by-match bonus scheme.
The players say they will not take part in the training and not to wear FIR sports equipment until an economic agreement has been reached for participation in the tournament.
Italy open their Pool D schedule against France at Twickenham on September 19, in a group which also includes Canada, Ireland and Romania, but their bosses are refusing to budge on the plan for a one-off bonus payment linked to full tournament performance.
An initial 40-strong squad gathered for Italy's June 14-July 3 camp near Bolzano, although captain Sergio Parisse and Martin Castrogiovanni were absent through French Top 14 play-off commitments.
In a statement, the FIR said: "The Italian Rugby Federation has taken note of the willingness expressed last night by the players called to the rally in Villabassa with the National Team, not to take part in the training and not to wear (FIR) sports equipment until reaching an economic agreement for participation in the summer preparation and the Rugby World Cup in September in England.
"The stance of last night does not change the will of the Federal Council - fully shared by the staff of the national team - to reach a financial settlement with the players based not on mere participation in international windows but on concrete meritocratic principles related to performance."
Wasps have completed their ninth signing of the off-season with prop James Johnston joining the club from Aviva Premiership rivals Saracens,
Johnston played 51 times for Saracens after joining them in 2013, having previously made more than a century of appearances for Harlequins.
The tight-head made his Tonga debut in 2008 and went on to amass 14 caps, helping his side lift the Pacific Nations Cup in 2012.
Johnston said: “When Wasps came in for me I had no hesitation. Having watched the changes the club has made in the past few seasons it is clear that Wasps are going places and I am really excited about being involved.
"There are clear ambitions for both the Aviva Premiership and the European Champions Cup and I’m really looking forward to being a part of that.”
The club's director of rugby Dai Young added “We’re really pleased to add James to our ranks ahead of the new season, having always been impressed with his performances against us, whether in a Saracens or a Harlequins shirt.
“His addition provides us with real depth and competition at tight-head, which is what you need at this level of the game.”
Jimmy Gopperth, Frank Halai, Dan Robson, George Smith, James Downey, Brendan Macken, Tom Bristow and Jamie Stevenson have also agreed deals with Wasps from the start of next season.
St Helens coach Keiron Cunningham was impressed with his young side’s 30-14 derby win over Wigan that took them back to the top of the First Utility Super League.
Saints trailed 10-8 at half-time but dominated the second half and took advantage of a series of errors by the visitors to run out comfortable winners at Langtree Park.
"In the second half we were ruthless," Cunningham said. "You've got to bear in mind we were playing against the best side in the competition on current form."It was a real good yardstick to see where we were at as a team. We've been chipping away at the points in the last few weeks, just growing that belief among ourselves and I think we really came of age tonight.
"We're in a really good place, I'm really pleased for them.
"There's an awful lot of passion around this game. You feel you actually deserve more than two points when you come away with the spoils.
"You feel like you should just walk away and win the league with that. What a spectacle for rugby league!"
St Helens captain Jon Wilkin shrugged off a head wound to lead his side to their impressive win, scoring the last of their five tries after pouncing on a wayward pass near his own line by Wigan centre Dan Sarginson.
"Considering he's a back rower playing seven, he was an absolute champion tonight," Cunningham said. "He led from the front. I thought he was absolutely outstanding."
Another player defying injury was hooker James Roby who played the full 80 minutes with bandages on both hands and proved to be a handful all night for his opponents.
"I always thought I was a pretty decent nine but I've never come close to this kid," Cunningham said.
"There's nothing like him in the competition. You take him for granted because he does that every week. He's an absolute machine."
It was still 14-14 when Joel Tomkins scored Wigan's third try on 50 minutes, adding to first-half scores from Joe Burgess and Sarginson, but they were left to rue two blunders by full-back Matty Bowen which gifted second-half tries to Shannon McDonnell and Travis Burns.
Take it on the chin
"There are other areas I'm just as upset about," said Wigan coach Shaun Wane.
"It was a poor team performance and it's a tough one to deal with.
"We just didn't play in the right areas of the field. It was an awful performance, we just never got into an arm wrestle and came up with silly errors and penalties. I'm really disappointed that we didn't challenge them in any area today.
"We didn't throw anything at them apart from the first six minutes.
"Without a doubt the best team won and it hurts really badly. We've got to take it on the chin."
Castleford's teenage winger Ashley Robson has signed a two-year contract extension that will keep him at the club until at least the end of 2017.
Robson, 19, who joined the Tigers from Leeds' academy, made his Super League debut at Salford in April when he scored the match-winning try.