Litmus test may refer to:

• Litmus test (chemistry), used to determine the acidity of a chemical solution
• Litmus test (politics), a question that seeks to find the character of a potential candidate by measuring a single indicator
• The Litmus Test, a Radio 4 programme presented by Fred Harris
• The Litmus Test, a 2004 album by Cut Chemist

• Acid test (disambiguation)
• Litmus Test of Medjugorje, the Catholic Church response to the Medjugorje apparitions
• Litmus milk, used to distinguish between different species of bacteria