The Royal Yacht 'Sírius' was commissioned by King Luís and Queen Maria Pia in 1876, and was launched on 14 April 1877. It was built in the Royal Galiots shed, in Junqueira, under the supervision of the commanding officer, Captain Lieutenant Carlos Sousa Folque Possolo; the construction was led by Tomás António Gonçalves, master carpenter from the Portuguese Navy’s Arsenal, and Diogo Jorge Batalha, construction demonstrator from the Naval Academy. After a few experiments, the yacht was offered to Queen Maria Pia.
The first regatta in which she participated was held on 4 September 1877; however, due to lack of wind, the competition was cancelled and repeated days later. However, the yacht was eventually disqualified for breaking the rules. It was considered to be the largest Royal yacht in Portugal, and King Luís decided to register her to participate in the Nice international regattas, where she became quite famous, not because of her participation, since she arrived late due to bad weather, but because on the return trip she competed with the French yacht Eugenie, beating her. Such an achievement earned her many compliments and several shipbuilders wanted to examine her construction in greater detail.
In 1887, the yacht Sírius was rigged as a pilot boat, and a few years later she was handed over to the Naval Academy to provide sailing instruction to midshipmen. In the 1930s, the yacht was transferred to 'Clube Náutico dos Oficiais e Aspirantes da Armada' and, after a few years on loan to the Naval Brigade, she returned to the Navy and was again used to provide sailing instruction and boarding internships to Navy Academy cadets. In 1983 she was handed over to the Maritime Museum, where she is currently on display.