According to Britain's Daily Mail newspaper, the actress gave birth to a baby boy earlier this week (ends19Jul20), and is currently resting at home with her family, including eldest son Silas, five, and her mother Kimberly Conroe Biel, who is supporting the couple.
The pair are thought to have been staying at their home in Big Sky, Montana, since 25 March (20) - when "The Illusionist" star shared the last snap of herself, showing the actress from a distance standing in a snowy valley surrounded by mountains.
Representatives for the couple have yet to officially confirm a new arrival for the pair.
The reports come just eight months after the "SexyBack" star was caught without his wedding ring as he spent a night getting close with his "Palmer" co-star Alisha Wainwright in New Orleans, Louisiana.
Onlookers reported the two stars appeared intoxicated as they held hands during their time together, with Timberlake later apologising to Biel for the indiscretion, which he called a "strong lapse in judgment."