The 32-year-old Oman international has only made one appearance for the Latics this season, in the League Cup defeat by Burton in August.
"With David Stockdale currently being injured, we felt it was important to bring in another experienced keeper," Brighton boss Sami Hyypia said.
"Ali certainly fits into this category as someone who has played at the top level for both Bolton and Wigan."
Brighton number one Stockdale missed his side's League Cup defeat by Tottenham on Wednesday with a finger injury.
Teenager Christian Walton deputised for the former Fulham man, making his senior debut for the Sussex club.
Al-Habsi made 28 appearances for Wigan last season but has been second in the pecking order behind Scott Carson this season.
"Last year he was fantastic but I made a decision this year to go with Scott," Wigan manager Uwe Rosler told BBC Radio Manchester.
"Ali has been absolutely professional.
"He is in my thoughts and in my plans but with such a class goalkeeper, at some point you have to give him games.
"I know his contract runs out at the end of the season and at some point we need to make a decision on that.
"We loan him initially for a month and after that we see where we are and how Ali feels.
"It is a gesture from us to support Ali because he has supported us and to give him competitive games."
Al-Habsi could make his debut for the Seagulls against Bournemouth on Saturday but he is ineligible to face his parent club at the Amex Stadium on Tuesday.
Brighton have signed Wigan goalkeeper Ali Al-Habsi on a one-month loan deal.