The 1903 painting, entitled Madame Valtat, went missing from the collector's private residence in Tokyo in 2000, along with five other works from the likes of Marc Chagall.
It was then sold at Sotheby's London in February 2013 for £1m ($1.6m). The present owner's identity will be kept confidential by the auction house, as is its policy.
The anonymous Japanese collector is thought to have notified police at the time of the sale, but did not register the work as missing on the stolen art database run by Interpol. As such, it escaped Sotheby's stringent checks, which are carried out before any work is sold.
The owner now intends to get the piece back, but may be unable to do so with ease, as Sotheby's has stated that the seller had acquired it legitimately in the year that it was stolen and was able to prove rightful ownership.
The portrait depicts Suzanne Valtat, the wife of Renoir's close friend and fellow artist Louis Valtat, and was given to her as a gift upon its creation.
In September, Heritage Auctions will hold a sale dedicated to the impressionist master, featuring an array of works and personal items from his career.
Paul Fraser Collectibles has a signed letter written by Pierre-August Renoir to his benefactor Madame Charpentier, who is wonderfully depicted in his masterpiece Madame Charpentier and her Children.