Claude Ambroise Régnier, duc de Massa (6 April 1746 – 24 June 1814), was a French lawyer and politician.

In 1769 Prince Louis of Salm-Salm called Régnier to Senones and made him his counselor and Attorney General, entrusting him with the administration of the principality.

After the flight of the king, on 22 June 1791 Régnier was sent as commissioner to the departments of the Rhine to receive the oaths of the troops.

[5] Régnier went underground during the Reign of Terror, only reappearing on the political scene after the promulgation of the Constitution of year III.

On 17 Brumaire year VIII (8 November 1799), he took part in a meeting at the house of Lemercier, Chairman of the Ancients, to prepare for the planned coup.

On the morning of 18 Brumaire he presented to the council a draft decree that transferred the two legislative chambers to Saint-Cloud.

[5] On 27 Fructidor year X (14 September 1802) Napoleon named Régnier chief judge and Minister of Justice, positions he held until 20 November 1813.