The company was established as the Phoenix Fire Office in 1782 by London sugar refiners discontented with the rates of premium charged by the established fire insurance offices. By 1783 it had 58 agencies, and the early success of the company meant that by 1790 it was able to establish minimum rates for insuring London riverside wharves and warehouses against fire. From 1782 the company started to insure overseas properties belonging to English merchants. Agents were appointed in France, Germany and Portugal in 1786-1787, and in New York and Montreal in 1804. Business in North America was extended further after an inspection tour in 1808-1809 by the company's secretary, Jenkin Jones. The hostilities of 1812-1814 led the company to withdraw from America, but it continued to develop its business in Canada and Europe. Growing competition in the U.K. forced Phoenix to become more competitive, and led to the purchase of a large number of small domestic local offices in the 1820s and 1830s to reduce the level of competition and develop the business. The 1860s also saw the company expand into Germany. In 1901 it was renamed the Phoenix Assurance Company Ltd.
Towards the end of the nineteenth century the company began to move into other forms of insurance, including life insurance (1895), accident business (1906) and marine insurance (1910). This diversification led Phoenix to acquire subsidiaries, such as Bradford Insurance (1959-1971), City Fire Office (1909-1925), Fortress Insurance (1953-1958), London Guarantee and Accident (1869-1922), Tariff Reinsurances (1919-1933) and Union Marine (1863-1911). Over time the company also amalgamated Dublin Insurance (c. 1770-1817), East Kent and Canterbury Economic Fire (1824-1828), Glasgow Fire (1803-1811), the fire business of Hertford, Cambridge and County Fire and Life (1824-1831), Law Life (1823-1909), Liverpool Fire (1776-1795), Manchester Fire (1771-1788), Metellus (1823-1839), National Union Society (1894-1904), Northampton Mutual Plate Glass (1902-1955), Palladium Fire (1824-1830), Pelican and British Empire (1903-1908), Plymouth Plate Glass (1909-1954), Protector Fire (1825-1836), Reading Fire (1823-1841), Royal Irish (1823) and Worcester Fire (1790-1817). Phoenix became a subsidiary of Sun Alliance in 1984.
In 1797 trustees of Phoenix Assurance established the Pelican Life Office. The firm became the Pelican Life Assurance Company, before merging with British Empire Mutual Life Assurance in 1903 to become the Pelican and British Empire Life Office. Pelican dealt in life assurance, annuities and (from 1847) group schemes, in the U.K., North America (from 1807) and overseas, operating through the country agencies of Phoenix Assurance. Over time Pelican acquired the business of Life Star (1818-1822) and Manchester Fire and Life (1824-1847). By the 1820s it had agents in France, Sweden, Germany and North America, and by the 1840s it had invested in the railways and offered short-term loans to docks and canals. The company also began to invest in foreign railways during the 1850s. Pelican amalgamated with Phoenix Assurance in 1907.