Teen Mom star Amber Portwood got inked -- and it's a tribute to her 2-year-old cutie Leah.

In a pic at Radaronline, the MTV star, 20, showed off a huge full-torso tattoo that's a rose-festooned portrait of her daughter with ex-fiance Gary Shirley.

The website reports that the stamp -- which appears unfinished in the pic -- is " a way to show her commitment to Leah."

After several weeks of living apart, little Leah was reunited with her mom Dec. 6 at Portwood's new home in Anderson, Ind. (Portwood's former home had been besieged with photographers and curious neighbors.)

Portwood "is so excited to have Leah back!" a source told Us shortly after the reunion.