"He’s here. Winter Mercy Morissette-Treadway. #8/8/19 #mywholelifeidreamedoflovingyouthree," Alanis, 45, captioned a photo of the infant.
Husband Mario "Souleye" Treadway shared the same image and gushed over his wife in the caption.
"@alanis you will forever be my heroine. Thank you for your warrior strength and ability to so deeply love," he wrote.
Alanis and Mario are also parents to daughter Onyx Solace, 3, and son Ever Imre, 8.
Just like his other two siblings, little Winter was born at home.
The couple tied the knot in May 2010. The Canadian songstress was previously engaged to actor Ryan Reynolds.
What do you think of Alanis' baby boy's unique name? Sound off in the comments below!