'Berthar' was the
mayor of the palace of
Neustria and
Burgundy from
686 to
687. He was the successor of
Waratton, whose daughter Anstrude he had married.
Unlike Waratton, however, Berthar did not have peace with
Pepin of Heristal. In
687, Pepin defeated him and
Theuderic III at
Tertry in the
Vermandois. Many fled to the nearby abbeys of
Péronne and
Saint Quentin. Berthar and Theuderic III withdrew themselves to
Paris. Pepin followed them and eventually forced a peace treaty with the condition that Berthar leave his office. In the ensuing quarrels, Berthar killed his mother-in-law Ansfled. Berthar fled. His wife married Pepin's eldest son
Drogo, duke of
Champagne, and Pepin became the mayor of the palace of Neustria and Burgundy without opposition.
Berthar died in either the
Autumn of
688 or early
689.