The monarchy of Solomon Islands is a system of government in which a hereditary monarch is the sovereign and head of state of Solomon Islands. The monarch and head of state, since 8 September 2022, is King Charles III. As sovereign, he is the personal embodiment of the Crown of Solomon Islands. Although the person of the sovereign is equally shared with 14 other independent countries within the Commonwealth of Nations, each country's monarchy is separate and legally distinct. As a result, the current monarch is officially titled King of Solomon Islands and, in this capacity, he and other members of the royal family undertake public and private functions domestically and abroad as representatives of Solomon Islands. However, the King is the only member of the royal family with any constitutional role.

All executive authority is vested in the monarch, and royal assent is required for the National Parliament of Solomon Islands to enact laws and for letters patent and Orders in Council to have legal effect. But the authority for these acts stems from the country's populace, in which sovereignty is vested, and the monarch's direct participation in any of these areas of governance is limited. Most of the powers are exercised by the elected members of parliament, the ministers of the Crown generally drawn from amongst them, and the judges and justices of the peace.

The Crown today primarily functions as a guarantor of continuous and stable governance and a nonpartisan safeguard against the abuse of power. While some powers are exercisable only by the sovereign, most of the monarch's operational and ceremonial duties are exercised by his representative, the governor-general of Solomon Islands.

In 1884, Germany annexed north-east New Guinea and the Bismarck Archipelago, and in 1886 they extended their rule over the North Solomon Islands. In 1886, Germany and Britain confirmed this arrangement, with the British gaining a "sphere of influence" over the southern Solomons. The British Solomon Islands Protectorate was declared in 1893, partly in response to abuses associated with labour recruitment and partly to regulate contacts between islanders and European settlers but mainly to forestall a threat of annexation by France. Colonial rule began in 1896. During World War II, the Solomon Islands campaign (1942–1945) saw fierce fighting between the United States, British Commonwealth forces and the Empire of Japan, including the Battle of Guadalcanal. After the war, Honiara on Guadalcanal became the new capital, replacing Tulagi. Subsequently, the Solomons set out on the path of constitutional development and decolonisation.

Appointed Executive and Legislative Councils were established in 1960, with a degree of elected Solomon Islander representation introduced in 1964 and then extended in 1967. A new constitution was drawn up in 1970 which merged the two Councils into one Governing Council, though the British Governor still retained extensive powers. A new constitution in 1974 reduced much of the Governor's remaining powers and created the post of Chief Minister, with full self-government for the territory achieved in 1976.

The original draft constitution of Solomon Islands passed by the Legislative Assembly in March 1977 provided for the country to become a republic one year after independence, unless a two-thirds majority in the national parliament voted to retain the monarchy. Following the transitional period the governor-general at the time would then become the inaugural president of the new republic. British officials opposed this formula on the grounds that it was too complicated and that Solomon Islands should choose its method of government upon independence. Negotiations in London in September 1977 between Solomons leaders and the British government produced a final draft constitution which omitted references to a republic. The British parliament's passage of the Solomon Islands Act 1978 allowed the country to become a sovereign state and an independent constitutional monarchy on 7 July 1978, with Queen Elizabeth II as head of state and Queen of Solomon Islands.

Prince Richard, Duke of Gloucester represented the Queen at the independence celebrations in July 1978. On 7 July, after the flag-raising ceremony, Baddeley Devesi and Peter Kenilorea took their oaths of office as governor-general and prime minister respectively. The Duke, who delivered his speech in Pijin, said: "Today onefella big day, hemi come now. Country belong you fella, hemi grow up, and Queen hemi wantim every something belong you fella. E come up goodfellow long or get a years, bye bye e come."

Solomon Islands is one of fifteen independent nations, known as Commonwealth realms, which shares its sovereign with other realms in the Commonwealth of Nations, with the monarch's relationship with Solomon Islands completely independent from his position as monarch of any other realm. Despite sharing the same person as their respective monarch, each of the Commonwealth realms — including Solomon Islands — is sovereign and independent of the others. The Solomon Island monarch is represented by a viceroy—the governor-general of Solomon Islands—in the country.