Louis Tomlinson: No DNA Test Needed ... Positive Freddie's His Son

Louis Tomlinson is so sure newborn son Freddie Reign is his kid, he has no plans to prove it with a DNA test ... TMZ has learned.

Sources close to Louis and Briana Jungwirth tell us the 1D-er's always copped to the kid being his ever since finding out Briana was pregnant. They started dating about a year ago and we're told things were so serious initially, he had zero doubt Briana was faithful.

While any lawyer would tell Tomlinson to seal the deal with a paternity test ... we're told he's totally cool with passing.