Ariana Grande Has Competition from Mac Miller's New Puppy

Mac Miller's gf, Ariana Grande, better hide her Louboutins ... the rapper has a new addition with sharp, destructive little teeth.

Sources close to Mac tell us he picked up a new pooch -- a 3-month-old pit mix he's named Myron. We're told Mac got him Sunday after seeing the pup in the window of Wylder's Holistic Pet Center & Rescue in Studio City.

Easy to see why Mac scooped him up -- the dog's really flippin' cute, and he'll be living it up. We're told Mac threw down about $1,200 for toys, food and treats.

Looks like Mac's finally recovering from having his last dog, Ralph, stolen 2 years ago. He offered a reward, but never got him back.

Keep Myron close, Mac ... he's too adorable.