3-Hydroxyaspartic acid (three letter abbreviation: Hya), also known as beta-hydroxyaspartic acid, is a derivative of aspartic acid which has been hydroxylated at position C3. The conjugated acid of 3-hydroxyaspartic acid is 3-hydroxyaspartate. The adjacent image shows <small>L</small>-threo-3-hydroxyaspartate.
Similarly to proteinogenic isoleucine and threonine, 3-hydroxyaspartic acid contains two chiral centers. As such, it can exist in 4 stereoisomers, which form two pairs of enantiomers.
The Hya amino acid residue is sometimes contained in EGF-like domains such as Vitamin K-dependent coagulation plasma proteins including protein C.
<small>D</small>-threo-3-Hydroxyaspartate is a part of the siderophore ornibactin.