Olivia Wilde is showing off her little one!

The 30-year-old actress took to Instagram Thursday to share a photo of herself wearing a "Rock and Roll" sweatshirt as she holds baby Otis, who is peering over his mama's back as she takes a walk.

"Rock and roll, baby," she captioned the sweet snapshot. 

The brunette beauty certainly seems to be enjoying motherhood, and she looks better than ever!

The "Her" star flaunted her post-baby bod at the H&M Flagship Fifth Avenue Store launch in New York City on Tuesday, rocking a black blazer, sheer navy blouse and black slacks.

The new mom -- who welcomed her son with Jason Sudeikis at the end of April -- is already back to her slender pre-baby figure.

Whatever she's been doing to get in shape ... it's definitely working! 

Click "Launch Gallery" at the top to see more cute celebrity kids, and check out the photos above to see more stars before and after giving birth.  

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