Also called Navy day, this holiday is always celebrated on 21 May.
In Chile it is known as 'Día de las Glorias Navales' and marks the date of the battle of Iquique on 21 May 1879.
The battle took place during the War of the Pacific between Chile and Peru.
The town of Iquique in the north of Chile was under Peruvian control. Chile had blockaded the port with two ships. In response, Peru sent two ships to break the blockade.
The Peruvian ships were more modern and the battle soon ended with defeat for the Chilean navy.
At first glance, this may not seem to be a great basis for a holiday celebrating the glories of the navy, but during the battle great courage was shown by the captain of one of the Chilean ships, Arturo Prat.
This bravery inspired many Chileans and following his death there was a large rise in the number of men enlisting in the navy. The legacy of Prat's heroism can be said to have led to the eventual victory of Chile in the War of the Pacific.
Nowadays Prat is still considered to be a national hero, and his name adorns many squares and streets across towns and cities in Chile and his portrait appears on the 10,000 Chilean peso bank note.
The day is marked by parades and speeches and marks the start of parliament, when the President of Chile will give the annual State of the Nation address.
On this day, most shops and businesses will be closed and there will be a reduced public transport service.