The 19-year-old actress and singer - who announced her engagement to The Hunger Games hunk Liam Hemsworth last month - has been snapped in a striped vest top that revealed the tattoo on the inside of her lower left arm.
According to X17Online.com the inking reads: "So that his place shall never be with those cold and timid souls who neither know victory nor defeat."
The quotation comes from Roosevelt's speech about Citizenship In A Republic that he gave in Paris in 1910. It refers to people who criticise others, while never attempting to do anything themselves.
It is thought to be Miley's 13th tattoo in her ever-growing collection.
Earlier this year she had "love never dies" tattooed further up her left arm.
Her other inkings include a tiny "love" tattoo in her right ear, the words "just breathe" above her left rib cage, a Hindu religious symbol of Om on her left wrist, a dreamcatcher on her side, an anchor on her right wrist and a skull on her ankle.
Miley also has five tiny tattoos on her fingers on her right hand: an equal sign, a peace symbol, a cross, a heart, and the word "karma".