The revelation came during the premiere of Deadpool & Wolverine in New York City on Monday night.
The 47-year-old actor took to the stage to thank his wife Blake, 36, and their four children, naming each one: James, Inez, Betty, and Olin.
This marked the first public mention of their youngest child’s name since the couple welcomed the baby in February 2023.
Ryan shared that their fourth child's name is Olin, a name of Nordic origin meaning "ancestor's heir" or "to inherit."
Despite Olin being traditionally a male name, the couple has not yet disclosed the gender of their newest addition.
Ryan and Blake are already parents to three daughters: nine-year-old James, seven-year-old Inez, and four-year-old Betty.
During his speech, Ryan acknowledged his family at the premiere and joked: “I hope that, if I'm lucky, this moment will be the most traumatic thing - that is, the contents of this movie - that happens in your wondrous lives.”
Blake made a stunning appearance at the event, wearing a dark red jumpsuit reminiscent of Ryan’s Deadpool character.
She completed her look with her blonde hair styled in a ponytail.
The couple never officially announced the birth of their fourth child. Instead, Blake subtly hinted at the new arrival on February 12, 2023, by sharing a photo of herself in fitted jeans and a top, noticeably without a baby bump.
The caption read: "Puppy Bowl Sunday 2023. Been busy," suggesting the addition to their family.
Blake first announced her fourth pregnancy in September 2022 at the 10th Annual Forbes Power Women’s Summit in New York City.
She later shared a series of pregnancy photos from 2022, including moments with her close friend Taylor Swift.
Ryan and Blake’s love story began in 2010 on the set of "Green Lantern."
They began dating in October 2011 and married on September 9, 2012, in South Carolina.
They welcomed their first child, James, in December 2014, followed by Inez in September 2016, Betty in October 2019, and their fourth child, Olin, in February 2023.
