Louis Antoine of France (1775-1844), Duke of Angoulême, Grand Admiral of France, visited Lorient on June 30, 1814. Architect Pierre Marie Lussault received an appointment to supervise construction of Saint-Louis Church. The mayor attended the coronation of Louis XVIII. This was also the year that the Count of Augier became Maritime Prefect of Lorient and the prison gained a hospital. Ducrest of Villeneuve commissioned the Diadem and the Magnificent.
Louis XVIII restored the old coat of arms of Lorient on November 8, 1815 – after the Hundred Days – the second reign of Emperor Napoleon I when he returned from exile on Elba and returned to power, only to be defeated by British Field Marshal Arthur Wellesley (1769-1852), 1st Duke of Wellington (1814-1852) and Prussian Field Marshal Gebhard Leberecht von Blücher (1742-1815) at the Battle of Waterloo (June 18, 1815). The next day, Louis XVIII issued a decree to suppress the Maritime Prefecture of Lorient. On December 15, 1815, he reogrnized the Royal Navy with twelve admirals and thirty-five ship captains.
On February 21, 1816, a royal decree restored the naval artillery. On March 30, 1816, a new police commissariat was established. On July 8, 1816, the brig Argus departed for Senegal, on a significant voyage because it rescued survivors of the Medusa. The French naval architect Stanislas Charles Henri-Laurent Depuy de Lôme (1816-1885) was born on October 15, 1816, at the Soyce Castle in Ploemeur, near Lorient. Construction of the lock bridge at Saint-Christophe stopped in 1816.
In 1817, in the aftermath of a donation by a Mr. Le Roux, a co-educational school was built over the old cemetery. On April 12, 1817, a brigade of gendarmerie – military policemen who policed the civilian population rather than the army – was garrisoned in the suburb of Kerentrech to act as night watch while the city gates were closed from 7:00 p.m. to 10:00 a.m. The Director of the Ponts et Chaussées (Bridges and Causeways) warned, on September 4, 1817, that a wooden bridge would have to be built at Saint-Christophe instead of the planned lock bridge to avoid silting the naval port. On November 29, 1817, plans to build a lazaretto (quarantine station for maritime travelers) on the island of Saint-Michel were approved. That same year, construction of a covered dock supported by sixteen granite columns began at the Arsenal de Lorient. It was later remodeled in 1820 and converted into a workshop.
The eighty-gun warship Neptune launched on March 21, 1818. The African, the French Royal Navy’s first steamship, was built in Lorient in 1818.
On March 1, 1819, the City Council voted to allocate toll revenue from the Saint-Christophe ferry on the Scorff River to fund the construction of a new timber bridge. This would happen for eighteen years, until January of 1841. A royal decree of July 28, 1819 authorized the construction of a wooden bridge at Saint-Christophe over the Scorff River. On November 15, 1819, the co-educational school replaced the free primary school. On November 25, 1819, the guardhouses at Merville and Kerentrech closed.
After 1794, no more merchant ships arrived in Lorient from Asia. After 1820, the French Royal Navy was the sole user of the port. While the French Navy – successively the French Royal Navy, the French Navy, the French Imperial Navy, and the French Navy – was the sole user of the port, the Navy used the northern part of the Arsenal and the left bank of the Scoff River and housed men in the southern part of the Arsenal, in what had been the commercial area. Barracks replaced the shops of the East India Company. In the 19th Century, the maritime prefecture was housed in the Hotel Gabriel, which Jacques V. Gabriel had designed to house the headquarters of the French East India Company.
In 1822, a secondary school opened. The shipyards gained a roofed slipway and drydock in 1824. A sardine cannery also opened up in Lorient that year. The lazaretto (quarantine station for maritime travelers) opened in 1825. That same year, a storm rendered both mills on the hill of Faouëdic were rendered inoperable.