Alexandre-Théodore Brongniart (February 15, 1739 – June 6, 1813) was a prominent French architect.

Born in Paris, France, Brongniart studied at the Lycée Condorcet. A prominent member of Parisian society, in 1767 he married Anne-Louise d'Egremont. The couple became friends of the royal portrait painter, Elisabeth Vigée-Lebrun who painted the portrait of their daughter, Alexandrine-Emilie Brongniart that now hangs in the National Gallery in London. During the Reign of Terror, Vigée-Lebrun hid in his home before fleeing the country.

Alexandre-Théodore Brongniart was also a close friend of Jean Antoine Houdon, the pre-eminent French sculptor of the day who sculpted busts of his daughter Alexandrine-Emilie and his son Alexandre Jr. that are now in the Louvre Museum in Paris. Brongniart Jr. went on to become a respected geologist and director of the famous Sèvres porcelain manufactory. In turn, his son Adolphe Theodore Brongniart became a famous botanist known as the father of paleobotany and a recipient of the Wollaston Medal in science.

Alexandre-Théodore Brongniart designed hotels, including the Hôtel de Condé and the Hotel de Monaco, and a number of exclusive private residences. In 1782 he was named architect and controller-general of the Ecole Militaire (Military School). In 1804, he was commissioned by Napoleon Bonaparte to create the layout for the famous Père Lachaise Cemetery. The Emperor was so pleased with his work that in 1807 he chose Brongniart to design the Paris Bourse (stock exchange). Brongniart did all of the designs but it would be his last work and he would not live to see the classical Greek styled building completed in 1825. The building was named "Palais Brongniart" in his honor and remains in use to this day.

Alexandre-Théodore Brongniart died in Paris in 1813 and was interred there in the cemetery he had designed.