The 22-year-old was the subject of significant transfer interest from Premier League club Leeds in the recently concluded transfer window.
Huddersfield supremo Phil Hodgkinson claimed that Leeds highest offer was worth up to £13m, while the Whites insist their final offer was £4m plus add-ons.
Regardless of the offers, Leeds could not reach an agreement with the Championship outfit over the transfer of the central midfielder.
Having stayed put at the John Smith’s Stadium in the summer, O’Brien has now put pen to paper on a new four-year contract with Huddersfield
The new deal, though, has a release clause in it that could see the midfielder leave the club if one of his suitors trigger it.
While Leeds were interested in signing O’Brien in the summer, it remains to be seen if they plan to return for him in the future.
It is also unclear how much the Elland Road outfit will have to pay to trigger the release clause should they decide to re-ignite their interest in O’Brien.