The Republic of Singapore Navy (RSN) is the maritime service branch of the Singapore Armed Forces (SAF) responsible for defending the country against any seaborne threats and as a guarantor of its sea lines of communications. The RSN traces its origins to the Royal Navy when Singapore was still a crown colony of the British Empire. The service was formally established in 1967, two years after its independence from Malaysia in 1965, and had undergone a substantial modernisation ever since – which has led them into becoming the most powerful navy in Southeast Asia.

The RSN also regularly conducts operations with the navies of its neighbouring countries to combat piracy and terrorist threats in the congested littoral waters of the Strait of Malacca and Singapore. It also jointly operates the Fokker 50 maritime patrol aircraft with its counterparts from the Republic of Singapore Air Force (RSAF) to provide air surveillance of the seaward approaches to Singapore, which is one of the busiest sealanes in the world. The RSN has engaged in international anti-piracy operations further abroad, partaking in the multinational Combined Task Force 151 off the Gulf of Aden.

Though numerically small in comparison to its much larger neighbours in terms of tonnage and manpower reserves, the RSN counteracts by continuously seeking to maintain a qualitative superiority over any adversary through the implementation of new technologies, fostering of alliances with extra-regional navies, and increased reliance on automation and unmanned assets. This has made the RSN one of the most sophisticated and well trained navies in the region. In addition, bilateral exercises with foreign navies are also held regularly.

All commissioned ships of the RSN have the ship prefix RSS standing for Republic of Singapore Ship.

The economy and defence are closely interlinked... We need the sea lanes to Singapore to be opened; hence a capable navy is crucial.

— Founding Prime Minister Lee Kuan Yew

As an island nation, the RSN forms part of Singapore's first line of defence. Its stated mission objectives are to:

The Republic of Singapore Navy traces its origins to the Royal Navy in the 1930s with only two patrol craft. The Straits Settlements Royal Naval Volunteer Reserve (SSRNVR) was established on 27 April 1934, and in 1941 became the Singaporean division of the Malayan Royal Naval Volunteer Reserve (MRNVR) during World War II. The service received several 75' motor launches built locally by John I. Thornycroft & Company Shipyard in Tanjong Rhu: HMS Pahlawan and the first HMS Panglima in 1937; the latter would later be sunk during the fall of Singapore in February 1942. A new 90' motor vessel bearing the name Panglima was launched in 1944, but upon its transfer to the MRNVR in 1948, proved unsuited for tropical waters and began deteriorating rapidly.