The 21-year-old, who made his Hull debut in a 1-0 UEFA Europa League qualifying defeat to Lokeren in August, has made six appearances in all competitions this term.
Maguire is seen as a replacement for Liam Ridgewell, who is set to return to the Portland Timbers for the start of the new MLS season.
"We are losing Liam Ridgewell after tomorrow's match and it was important we moved fast to replace him," said Wigan manager Malky Mackay on Tuesday.
"Harry is someone I have admired for a long time and I thank Steve [Bruce] for allowing him to continue his development with us.
"He's a powerful player with a lot of experience for his age and he fits the profile of the players we want to bring in; young, hungry and desperate to play."
Wigan sit 23rd in the Championship, just two points clear of basement club Blackpool.
