Jaurès was born at Castres, Tarn.
After his studies at the École Navale, Louis Jaurès took part in the trials of the Gymnote. In 1903, Jaurès was capitaine de frégate, in command of the Galilée; he was sent to rescue five sailors abandoned in Africa by their employer, Jacques Lebaudy, who was attempting to establish his own country, the "Empire of the Sahara".
Jaurès later took command of the Gloire. The ship suffered an accidental explosion on 20 September 1911 which caused limited damage.
Promoted to capitaine de vaisseau, Jaurès took command of the first-rank battleship Liberté on 24 November 1910. On 25 September 1911, as Jaurès was on shore leave, the Liberté was destroyed by an accidental explosion. He was put on trial and slandered by the right-wing press, but was acquitted by the court martial.