Adele Bloch-Bauer
According to Klimt's website, Bloch-Bauer was his mistress.  She is also the only woman he ever painted twice. Adele's husband, Ferdinand Bloch-Bauer, hired Klimt to paint both paintings. Klimt painted Portrait of Adele Bloch-Bauer I in 1907 and Portrait of Adele Bloch-Bauer II in 1912. Some artists also think Adele Bloch-Bauer might be the woman in The Kiss and Judith and the Head of Holofernes.  The first portrait was a gift from Ferdinand Bloch-Bauer to Adele's parents.