Tris, or tris(hydroxymethyl)aminomethane, or known during medical use as tromethamine or THAM, is an organic compound with the formula (HOCH2)3CNH2. It is extensively used in biochemistry and molecular biology as a component of buffer solutions such as in TAE and TBE buffers, especially for solutions of nucleic acids.

In medicine, tromethamine is occasionally used as a drug, given in intensive care for its properties as a buffer for the treatment of severe metabolic acidosis in specific circumstances.