TMZ reported model Michael Girgenti filed legal documents, claiming he fathered Kardashian's son in 2009 and requesting a paternity test.
"After 3 1/2 years of rumors and lies being spread by an individual I met briefly at a photo shoot, I am setting the record straight that Scott is Mason's father," Kourtney told UsMagazine.com Thursday. "While it saddens me to have to address these ridiculous lies -- especially when the truth was never in doubt -- this story must be put to rest."
Kardashian and Disick also have a 13-month-old daughter named Penelope.
Duggar sisters unveil Christian dating rules in new book
McPhee, Cokas 'working on their marriage' after affair