The powerful Wales international, who grew up in nearby Pontefract and played for Castleford junior club Townville Tigers, could debut against Hull KR on Sunday.
His arrival is a major coup for the Super League club – he played in last year’s Grand Final while on a season-long loan at Wigan Warriors – and will certainly bolster coach Daryl Powell’s options.
Patrick, 27, can operate at prop, second-row or loose forward and his loss will be keenly felt by bottom-placed Huddersfield who have been unable to persuade him to stay next season.
Powell said: “It’s definitely a big boost getting a player of Larne’s calibre in. He’s highly-rated in the game and has played at a couple of clubs right up at the top in the last few years.
“In terms of experience and the way he plays – I like that as he’s really quick, has good late feet at the line and is a tough defender who gets off the line and hits people – it’s a really good signing for us.
Patrick, who was part of the Bradford Bulls academy, earned his first taste of Super League with Huddersfield and played more than 100 games for the Fartowners, winning the League Leaders’ Shield with them in 2013.
Huddersfield managing director Richard Thewlis said: “Clearly this is a loss to us and many will be sad to see Larne leave us. But as we would have been unable to agree terms within our cap with him for a longer stay beyond this year we believe it in both parties best interests to make the move now.
“Hopefully from Larne’s perspective a fresh environment will re-vitalise him and get him back to his form of a few years back.
“For our part the freeing up of paid salary cap space will allow us to consider players who may become available.“