A colonial empire is a collective of territories (often called colonies), either contiguous with the imperial center or located overseas, settled by the population of a certain state and governed by that state.
Before the expansion of early modern European powers, other empires had conquered and colonized territories, such as the Romans in Iberia, or the Chinese in what is now southern China. Modern colonial empires first emerged with a race of exploration between the then most advanced Europe maritime power, Portugal and Spain, during the 15th century. The initial impulse behind these dispersed maritime empires and those that followed was trade, driven by the new ideas and the capitalism that grew out of the European Renaissance. Agreements were also made to divide the world up between them in 1479, 1493, and 1494. European imperialism was born out of competition between European Christians and Ottoman Muslims, the latter of which rose up quickly in the 14th century and forced the Spanish and Portuguese to seek new trade routes to India, and to a lesser extent, China.
Although colonies existed in classical antiquity, especially amongst the Phoenicians and the Ancient Greeks who settled many islands and coasts of the Mediterranean Sea, these colonies were politically independent from the city-states they originated from, and thus did not constitute a colonial empire.
Portugal began establishing the first global trade network and one of the first colonial empires  under the leadership of Henry the Navigator. The empire spread throughout a vast number of territories distributed across the globe (especially at one time in the 16th century) that are now parts of 60 different sovereign states. Portugal would eventually control Brazil, territories such as what is now Uruguay and some fishing ports in north, in the Americas; Angola, Mozambique, Portuguese Guinea, and São Tomé and Príncipe (among other territories and bases) in the North and the Subsaharan Africa; cities, forts or territories in all the Asian Subcontinents, as Muscat, Ormus and Bahrain (amongst other bases) in the Persian Gulf; Goa, Bombay and Daman and Diu (amongst other coastal cities) in India; Portuguese Ceylon; Malacca, bases in Southeast Asia and Oceania, as Makassar, Solor, Banda, Ambon and others in the Moluccas, Portuguese Timor; and the granted entrepôt-base of Macau and the entrepôt-enclave of Dejima (Nagasaki) in East Asia, amongst other smaller or short-lived possessions.
During its Siglo de Oro, the Spanish Empire had possession of Mexico, South America, the Philippines, all of southern Italy, a stretch of territories from the Duchy of Milan to the Netherlands, Luxembourg, and Belgium, parts of Burgundy, and many colonial settlements in the Americas, Africa, and Asia. Possessions in Europe, Africa, the Atlantic Ocean, the Americas, the Pacific Ocean, and East Asia qualified the Spanish Empire as attaining a global presence. From 1580 to 1640 the Portuguese Empire and the Spanish Empire were conjoined in a personal union of its Habsburg monarchs during the period of the Iberian Union, but beneath the highest level of government, their separate administrations were maintained.
Subsequent colonial empires included the French, English, Dutch and Japanese empires. By the mid-17th century, the Tsardom of Russia, continued later as the Russian Empire and the Soviet Union, became the largest contiguous state in the world, and the modern Russian Federation continues to be so to this day. Russia today has nine time zones, stretching across about half of the world's longitude.
The British Empire, consolidated during the period of British maritime hegemony in the 19th century, became the largest empire in history by virtue of the improved transportation technologies of the time. At its height, the British Empire covered a quarter of the Earth's land area and comprised a quarter of its population. During the New Imperialism, Italy and Germany also built their colonial empires in Africa.
It is worth noting that, from the 16th to 19th century, there were also large non-European empires, most notably the Qing Empire of China, which conquered a huge area of East and Inner Asia, and the states of the Age of the Islamic Gunpowders, Mughal India, Ottoman Turkey, and Savafid Iran. The British replaced the Mughals in India, and after the Boxer Rebellion in 1901, Imperial China made concessions to the Eight-Nation Alliance (all the Great Powers of the time). By the end of the 20th century most of the previous colonial empires had been decolonized, though the modern nation-states of Russia and China inherited much of the territory of the Romanov and Qing empires, respectively.
The chart below shows the span of some European colonial empires.
Other countries with colonial possessions:
Directly controlled territory of the United States at its greatest extent (1898–1902)
Austro-Hungarian colonies and concessions throughout history
Duchy of Courland and Semigallia
Couronian settlements in Africa
Map of the Hospitaller order's territories in the Caribbean
Couronian settlements in Americas (New Courland on Tobago)
Map of Morocco and Western Sahara with the Southern Provinces in a darker color.