The musician, who recently tied the knot with actor and fellow vegan Liam Hemsworth, took to social media to dismiss the rumors.
According to OK! Australia, an unnamed source said: "Miley’s over the moon because she’s carrying Liam’s baby… It’s a girl, which is what [they] hoped for."
But this is untrue, said Cyrus, via a Twitter post, where she photoshopped an egg over her stomach.
"I'm not 'Egg-xpecting' but it's 'Egg-celent' to hear everyone is so 'Happy For Us' .... we’re happy for us too," she wrote.
"'Egg-cited' for this next chapter in our lives.... Now, can everyone leave me alone and go back to staring at an egg."
Love letter to Liam
The rumors follow a heartfelt open letter Cyrus shared with husband Hemsworth on his 29th birthday.
"I thought I could share some of my favorite things about my favorite dude in honor of this very special day. The way you look at me, the way you look at our dogs, our pigs, our horses, our cats, our fish.
"I love how you learn and grow. I love writing songs about you on the piano. I love how you let ME be ME. Put simply…. I love YOU. Unconditionally. In our time together you have displayed who it really means to love thru all circumstances.
"I respect you and you respect me. If the world had more of this type of understanding we wouldn’t be building more walls but bridges….I’m proud of the person you have become and look forward all the good we will contribute ToGeThEr in the future."