The 18th century saw the newly united Great Britain rise to be the world's dominant colonial power, with France becoming its main rival on the imperial stage. Great Britain, Portugal, the Netherlands, and the Holy Roman Empire continued the War of the Spanish Succession, which lasted until 1714 and was concluded by the Treaty of Utrecht. Philip V of Spain renounced his and his descendants' claim to the French throne, and Spain lost its empire in Europe. The British Empire was territorially enlarged: from France, Britain gained Newfoundland and Acadia, and from Spain Gibraltar and Menorca. Gibraltar became a critical naval base and allowed Britain to control the Atlantic entry and exit point to the Mediterranean. Spain ceded the rights to the lucrative asiento (permission to sell African slaves in Spanish America) to Britain. With the outbreak of the Anglo-Spanish War of Jenkins' Ear in 1739, Spanish privateers attacked British merchant shipping along the Triangle Trade routes. In 1746, the Spanish and British began peace talks, with the King of Spain agreeing to stop all attacks on British shipping; however, in the Treaty of Madrid Britain lost its slave-trading rights in Latin America.

In the East Indies, British and Dutch merchants continued to compete in spices and textiles. With textiles becoming the larger trade, by 1720, in terms of sales, the British company had overtaken the Dutch. During the middle decades of the 18th century, there were several outbreaks of military conflict on the Indian subcontinent, as the English East India Company and its French counterpart, struggled alongside local rulers to fill the vacuum that had been left by the decline of the Mughal Empire. The Battle of Plassey in 1757, in which the British defeated the Nawab of Bengal and his French allies, left the British East India Company in control of Bengal and as the major military and political power in India. France was left control of its enclaves but with military restrictions and an obligation to support British client states, ending French hopes of controlling India. In the following decades the British East India Company gradually increased the size of the territories under its control, either ruling directly or via local rulers under the threat of force from the Presidency Armies, the vast majority of which was composed of Indian sepoys, led by British officers. The British and French struggles in India became but one theatre of the global Seven Years' War (1756–1763) involving France, Britain, and the other major European powers.

The signing of the Treaty of Paris of 1763 had important consequences for the future of the British Empire. In North America, France's future as a colonial power effectively ended with the recognition of British claims to Rupert's Land, and the ceding of New France to Britain (leaving a sizeable French-speaking population under British control) and Louisiana to Spain. Spain ceded Florida to Britain. Along with its victory over France in India, the Seven Years' War therefore left Britain as the world's most powerful maritime power.