This invention provides a novel process for producing optically active 3-hydroxy-.gamma.-butyrolactone in a short step, which is superior economically and in efficiency and industrially suitable by using a starting material which is inexpensive and easily available and reagents easy to handle. This invention relates to a process for producing optically active 3-hydroxy-.gamma.-butyrolactone represented by formula I: ##STR1## wherein the symbol * means an asymmetric carbon atom, which comprises hydrogenating an optically active 4-substituted oxy-3-hydroxybutyrate represented by formula II: ##STR2## wherein R.sup.1 represents a C.sub.1-4 lower alkyl group, R.sup.2 represents a protective group for a hydroxyl group deprotected by hydrogenation with a heterogeneous hydrogenation catalyst, and the symbol * has the same meaning as defined above, in the presence of a heterogeneous hydrogenation catalyst and an acidic substance followed by deprotection and simultaneous ring closure thereof.