Zookeepers at Chicago's Lincoln Park Zoo confirm the latest addition to the primate house is male.
The white-cheeked baby gibbon was born in January, but its sex hadn't been determined.
Lincoln Park Zoo Curator of Primates Maureen Leahy says the little guy has been named Sai.
It means "son" in Burmese.
Zookeepers say the 3-month-old is starting to test out his long arms on hanging vines.