International English is the concept of using the English language as a global means of communication similar to an international auxiliary language, and often refers to the movement towards an international standard for the language. Related and sometimes synonymous terms include: Global English, World English, Continental English, General English and Common English^{[citation needed]}. These terms may describe the fact that English is spoken and used in numerous dialects around the world or refer to a desired standardisation (i.e. Standard English).

There have been many proposals for making International English more accessible to people from different nationalities but there is no consensus; Basic English is an example, but it failed to make progress. More recently, there have been proposals for English as a lingua franca (ELF) in which non-native speakers take a highly active role in the development of the language.

The modern concept of "International English" does not exist in isolation, but is the product of centuries of development of the English language.

The English language evolved in England, from a set of West Germanic dialects spoken by the Angles and Saxons, who arrived from continental Europe in the 5th century. Those dialects became known as Englisc (literally "Anglish"), the language today referred to as Anglo-Saxon or Old English (the language of the poem Beowulf). However, less than a quarter of the vocabulary of Modern English is derived from the shared ancestry with other West Germanic languages because of extensive borrowings from Norse, Norman, Latin, and other languages. It was during the Viking invasions of the Anglo-Saxon period that Old English was influenced by contact with Norse, a group of North Germanic dialects spoken by the Vikings, who came to control a large region in the North and East of England known as the Danelaw. Vocabulary items entering English from Norse (including the pronouns they and them) are thus attributable to the on-again-off-again Viking occupation of Northern and Eastern England during the centuries prior to the Norman Conquest (see, e.g., Canute the Great). Soon after the Norman Conquest of 1066, the Englisc language ceased being a literary language (see, e.g., Ormulum) and was replaced by Anglo-Norman as the written language of England. During the Norman Period, English absorbed a significant component of French vocabulary (approximately one-third of the vocabulary of Modern English). With this new vocabulary, additional vocabulary borrowed from Latin (with Greek, another approximately one-third of Modern English vocabulary, though some borrowings from Latin and Greek date from later periods), a simplified grammar, and use of the orthographic conventions of French instead of Old English orthography, the language became Middle English (the language of Chaucer). The "difficulty" of English as a written language thus began in the High Middle Ages, when French orthographic conventions were used to spell a language whose original, more suitable orthography had been forgotten after centuries of nonuse. During the late medieval period, King Henry V of England (lived 1387–1422) ordered the use of the English of his day in proceedings before him and before the government bureaucracies. That led to the development of Chancery English, a standardised form used in the government bureaucracy. (The use of so-called Law French in English courts continued through the Renaissance, however.)

The emergence of English as a language of Wales results from the incorporation of Wales into England and also dates from approximately this time period. Soon afterward, the development of printing by Caxton and others accelerated the development of a standardised form of English. Following a change in vowel pronunciation that marks the transition of English from the medieval to the Renaissance period, the language of the Chancery and Caxton became Early Modern English (the language of Shakespeare's day) and with relatively moderate changes eventually developed into the English language of today. Scots, as spoken in the lowlands and along the east coast of Scotland, developed largely independent of Modern English, and is based on the Northern dialects of Anglo-Saxon, particularly Northumbrian, which also serve as the basis of Northern English dialects such as those of Yorkshire and Newcastle upon Tyne. Northumbria was within the Danelaw and therefore experienced greater influence from Norse than did the Southern dialects. As the political influence of London grew, the Chancery version of the language developed into a written standard across Great Britain, further progressing in the modern period as Scotland became united with England as a result of the Acts of Union of 1707.

English was introduced to Ireland twice—a medieval introduction that led to the development of the now-extinct Yola and Fingallian dialects, and a modern introduction in which Hiberno-English largely replaced Irish as the most widely spoken language during the 19th century, following the Act of Union of 1800. Received Pronunciation (RP) is generally viewed as a 19th-century development and is not reflected in North American English dialects (except for an affected Transatlantic accent of the early to mid-20th century), which are based on 18th-century English.

The establishment of the first permanent English-speaking colony in North America in 1607 was a major step towards the globalisation of the language. British English was only partially standardised when the American colonies were established. Isolated from each other by the Atlantic Ocean, the dialects in England and the colonies began evolving independently.

The British colonisation of Australia starting in 1788 brought the English language to Oceania. By the 19th century, the standardisation of British English was more settled than it had been in the previous century, and this relatively well-established English was brought to Africa, Asia and New Zealand. It developed both as the language of English-speaking settlers from Britain and Ireland, and as the administrative language imposed on speakers of other languages in the various parts of the British Empire. The first form can be seen in New Zealand English, and the latter in Indian English. In Europe, English received a more central role particularly since 1919, when the Treaty of Versailles was composed not only in French, the common language of diplomacy at the time, but, under special request from American president Woodrow Wilson, also in English – a major milestone in the globalisation of English.^{[citation needed]}