Pierre Clément de Laussat (23 November 1756 – 10 April 1835) was a French politician, and the 24th Governor of Louisiana, the last under French rule.
Laussat was born in the town of Pau. After serving as receveur général des finances in Pau and Bayonne, he was imprisoned during the Terror, but was released and recruited in the armée des Pyrénées. On April 17, 1797, he was elected to the Council of Ancients. After the coup of 18 Brumaire, he entered the Tribunat on December 25, 1799.
He was appointed by Napoleon Bonaparte to be colonial prefect (governor) of Louisiana in 1802 and arrived in the colony on March 26, 1803, just two weeks before Napoleon made his decision to sell Louisiana to the United States. Laussat was initially only to be the interim head of Louisiana until arrival of the Governor General Jean-Baptiste Bernadotte appointed by Napoleon. However, news of the Louisiana Purchase reached Bernadotte before he could sail from La Rochelle in May 1803. For several months Laussat ruled as a normal governor, first abolishing the local cabildo and then publishing the Napoleonic Code in the colony.
Within several months, he heard that Louisiana had been sold to the U.S. but he did not believe it. On July 28, 1803, he wrote to the French government to inquire whether the rumor was true. On August 18, 1803, he received word from Napoleon that France had declared war on Great Britain and that he was to transfer Louisiana to the United States.