The 37-year-old television personality is expecting her first child with her boyfriend, Slipknot member Sid Wilson.
Osbourne shared the news Thursday on Instagram alongside a photo of herself holding up a sonogram.
"I know that I have been very quiet these past few months so I thought I would share with you all as to why... I am over the moon to announce that I am going to be a Mumma. To say that I am happy does not quite cut it. I am ecstatic!" she captioned the post.
Osbourne's mom, television personality Sharon Osbourne, posted the same photo on her own account.
"My [heart] could not be more full! So excited to share the beautiful journey ahead with you @kellyosbourne," Sharon Osbourne wrote.
The Hills alum Audrina Patridge and former Jersey Shore star Nicole "Snooki" Polizzi were among those to congratulate Osbourne in the comments.
"congrats Kelly!!!!!! So excited for you your going to be such an amazing momma," Patridge said.
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"Omg congrats mawma!" Polizzi added.
Osbourne and Wilson reportedly met while attending Ozzfest, a music festival organized by Osbourne's parents, Ozzy Osbourne and Sharon Osbourne, in 1999. The couple were first romantically linked in January.
"Kelly and Sid met when his band was touring with Ozzfest in 1999," a source told People at the time. "They have remained friends since. They are very happy together."
Osbourne came to fame on her family's reality series The Osbournes and has since appeared on Dancing with the Stars, Fashion Police, Project Runway Junior and The Masked Singer.
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