Subprime lender Springleaf Holdings Inc. is nearing a deal to buy Citigroup Inc.’s OneMain Financial for about $4.25 billion, said people familiar with the matter. The deal is expected to be announced as soon as Tuesday, the people said. OneMain makes small subprime loans to U.S. customers. Getting rid of the unit has long been a goal for Citigroup C, -0.06% Representatives for SpringleafLEAF, -0.20% and Citigroup declined to comment. Plans to get rid of OneMain date back to at least 2009, when Citigroup was trying to remake itself into a smaller, easier-to-manage operation after the financial crisis. But potential deals to sell the unit fell through when Citigroup didn’t want to sell for too low a price or when investors grew concerned about the ability to raise funding for the deal. An expanded version of this report appears at WSJ.com.