The Assyrian continuity thesis is the idea that the modern Assyrians are to be culturally and historically identified with, and are the direct descendants of, the ancient Assyrians, who were one of several contemporary civilizations in Mesopotamia. This claimed heritage is a key aspect of the modern Assyrian identity. The modern Assyrian people are an ethno-linguistic and religious minority in their ancestral homeland, which spans parts of Iraq, northeastern Syria, southeastern Turkey, and northwestern Iran.

Assyrian culture and identity appear to have survived the violent collapse of the Neo-Assyrian Empire in 609 BC. During the long post-imperial period (6th century BC – 3rd century AD), when Assyria was also known as Athura, Provincia Assyria, and Asoristan, the Akkadian language gradually went extinct, completely disappearing by the 1st century AD. However, other aspects of the Assyrian civilization, such as religion, traditions, naming patterns, and the Akkadian-influenced dialects of East Aramaic survived in a reduced but recognizable form, before giving way to specifically native forms of Eastern Rite Christianity.Frahm, Eckart (2023). "Assyria's Legacy on the Ground". Assyria: The Rise and Fall of the World's First Empire. Basic Books. p. 353. Boldt, Andreas D. (2017). Historical Mechanisms: An Experimental Approach to Applying Scientific Theories to the Study of History. Routledge. p. 154.

The gradual extinction of Akkadian and its replacement with Akkadian-influenced East Aramaic does not reflect the disappearance of the original Assyrian population; Aramaic was used not only by settlers, but also by native Assyrians and Babylonians, in time even becoming used by the royal administrations of Assyria and Babylonia themselves, and indeed retained by the succeeding Indo-European–speaking Achaemenid Empire. In fact, the new language of the Neo-Assyrian Empire, the Imperial Aramaic, was itself a creation of the Assyrian Empire and its people, and with its retention of an Akkadian grammatical structure and Akkadian words and names, is distinct from the Western Aramaic of the Levant which gradually replaced the Canaanite languages (with the partial exception of Hebrew). In addition, Aramaic also replaced other Semitic languages such as Hebrew, Phoenician, Arabic, Edomite, Moabite, Amorite, Ugarite, Dilmunite, and Chaldean among non-Aramean peoples without prejudicing their origins and identity. Since the Aramaic language was so deeply integrated into the empire and due to the fact it was spread chiefly by Assyria, in later Demotic Egyptian, Greek, and Mishanic Hebrew texts it was referred to as the "Assyrian writing." Due to assimilation efforts encouraged by Assyrian kings, fellow Semitic Arameans, Israelites, Judeans, Phoenicians, and other non-Semitic groups such as Hittites, Hurrians, Urartians, Phrygians, Persians, and Elamites deported into the Assyrian heartland are also likely to quickly have been absorbed into the native population, self-identified, and been regarded, as Assyrians. The Assyrian population of Upper Mesopotamia was largely Christianized between the 1st and 4th centuries AD, however Mesopotamian religion enduring among Assyrians in small pockets until the late Middle Ages, a further indication of continuity. Assyrian Aramaic-language sources from the Christian period predominantly use the self-designation Suryāyā ("Syrian") alongside "Athoraya", with early medieval Arab, Persian and Armenian sources using the derivative terms "Sūryānīyūn", "Asori" and "Assuri" respectively. The term Suryāyā, sometimes alternatively translated as "Syrian" or "Syriac", is generally accepted to derive from the ancient Akkadian Assūrāyu, meaning Assyrian. The academic consensus is that the modern name "Syria" originated as a shortened form of "Assyria" and applied originally only to Mesopotamian Assyria and not to the modern Levantine country of Syria. Christian Palestinian Aramaic texts, presumably with Greek influence, use the term "Suraya" and "Asuraya" interchangeably to refer to the ancient Assyrians.

Assyrian nationalism centered on a desire for self-determination developed near the end of the 19th century, coinciding with increasing contacts with Europeans, increasing levels of ethnic and religious persecution, along with increased expressions nationalism in other Middle Eastern groups, such as the Arabs, Armenians, Copts, Jews, Kurds, Persians, and Turks. Through the large-scale promotion of long extant terms and promotion of identities such as ʾĀthorāyā and ʾAsurāyā, Assyrian intellectuals and authors hoped to inspire the unification of the Assyrian nation, transcending long-standing religious denominational divisions between the Assyrian Church of the East, its 17th century offshoot, the Chaldean Catholic Church, the Syriac Orthodox Church, and various smaller largely Protestant denominations. This effort has been met with both support and some opposition from various religious communities; some denominations have rejected unity and promoted alternate religious identities, such as "Aramean", "Syriac", and "Chaldean". Though some religious officials and activists (particularly in the west) have promoted such identities as separate ethnic groups rather than simply religious denominational groups, they are not generally treated as such by international organizations or historians, and historically, genetically, geographically and linguistically these are all the same Assyrian people.

Many scholars in various fields have expressed support for Assyrian continuity.See the scholars listed in the Academia and politics section. There is also some opposition, especially in the field of Syriac studies.. According to the leading Syriac scholar Sebastian Brock, "the alleged ethnic identity with the ancient Assyrians is in fact a recent creation which has taken place in the course of the last century and a half, and it lacks any sound historical basis.". According to Adam H. Becker, a Syriac scholar who has investigated the origins of Assyrian nationalism, the use of the word Assyrian itself for the modern ethnic group "derives from Western sources, not from a continuity of identity between the ancient Assyrians and the modern ones.". Proponents of the thesis regard such statements as inaccurate and partial..

Assyrians after the Assyrian Empire

Early assumption of Assyrian annihilation

Ancient Assyria fell in the late 7th century BC through the Medo-Babylonian conquest of the Assyrian Empire, with most of its major population centers violently sacked. In the millennia following the fall of Assyria, knowledge of the ancient empire chiefly survived in western literary tradition through accounts of Assyria in the Hebrew Bible and works by classical authors, both of which described Assyria's fall as violent and comprehensive destruction. Before the 19th century, the prevalent belief in Biblically influenced western scholarship was that ancient Assyria and Babylonia had been literally annihilated due to provoking divine wrath. This belief was reinforced through archaeologists in the Middle East initially not finding many remains fitting with the conventional European image of ancient cities, with stone columns and great sculptures, beyond those of ancient Persia; Assyria and other Mesopotamian civilizations left no magnificent ruins above ground—all that remained to see were huge grass-covered mounds in the plains which travellers at times believed to simply be natural features of the landscape. Early European archaeologists in the Middle East were also for the most part more interested in confirming Biblical truth through their excavations than to spend time on new interpretations of the evidence they discovered.

Though the Bible and other Hebrew texts describe the destruction of the Assyrian Empire, they do not actually claim that the Assyrian people were destroyed or replaced. The 2nd century BC apocryphal Book of Judith states that the Neo-Babylonian king Nebuchadnezzar II (605–562 BC) "ruled over the Assyrians in the great city of Nineveh", the Book of Ezra refers to the Persian king Darius I as "king of Assyria", and the Book of Isaiah states that there will come a day when God will proclaim "Blessed be Egypt my people, and Assyria the work of my hands, and Israel my heritage". The erroneous idea of complete Assyrian annihilation, despite increasing evidence to the contrary, proved to be enduring in western academia. As late as 1925, the Assyriologist Sidney Smith wrote that "The disappearance of the Assyrian people will always remain a unique and striking phenomenon in ancient history. Other, similar kingdoms and empires have indeed passed away, but the people have lived on ... No other land seems to have been sacked and pillaged so completely as was Assyria". Just a year later, Smith had completely abandoned the idea of the Assyrians having been eradicated and recognized the persistence of Assyrians through the Christian period into the present.

Post-imperial Assyria in modern Assyriology

Modern Assyriology does not support the idea that the fall of Assyria also brought with it an eradication of the Assyrian people and their culture. Though in the past regarded as a "post-Assyrian" age, Assyriologists today consider the last period of ancient Assyrian history to be the long post-imperial period, extending from 609 BC to around AD 250 with the destruction of the semi-independent Assyrian states of Assur, Osroene, Adiabene, Beth Nuhadra and Beth Garmai by the Sassanid Empire, or to the end of Sassanid ruled Asoristan (Assyria) and the Islamic Conquest around 637 AD, and support a continuity into the present day.

Though the centuries that followed the fall of Assyria are characterized by a distinct lack of surviving sources from the region, at least in comparison to previous eras, the idea that Assyria was rendered uninhabited and desolated stems from the contrast with the richly attested Neo-Assyrian period, not from the actual extant written sources from the post-imperial period, which although reduced, remain unbroken through to the modern era.

Though the Assyrian bureaucracy and governmental institutions disappeared with Assyria's fall, Assyrian population centers and culture did not. At Dur-Katlimmu, one of the largest settlements along the Khabur river, a large Assyrian palace, dubbed the "Red House" by archaeologists, continued to be used in Neo-Babylonian times, with cuneiform records there being written by people with Assyrian names, in Assyrian style, though dated to the reigns of the early Neo-Babylonian kings. These documents mention officials with Assyrian titles and invoke the ancient Assyrian national deity Ashur. Two Neo-Babylonian texts discovered at the city of Sippar in Babylonia attest to there being royally appointed governors at both Assur and Guzana, another Assyrian site in the north. Arbela is attested as a thriving Assyrian city, but only very late in the Neo-Babylonian period, and there were attempts to revive the city of Arrapha in reign of Neriglissar (560–556 BC), who returned a cult statue to the site. Harran was revitalized, with its great temple dedicated to the lunar god Sîn being rebuilt under Nabonidus whose mother was an Assyrian priestess from that city. (556–539 BC). In nearby Edessa, Assyrian religious traditions also survived well into the common era.Frahm, Eckart (2023). "Assyria's Legacy on the Ground". Assyria: The Rise and Fall of the World's First Empire. Basic Books. p. 357. Even in certain regions beyond the Euphrates, the legacy of Assyria endured, such as in Hierapolis where Shalmaneser had once settled many Assyrians. By at least the second century CE, the memory of Semiramis and Sardanapalus was faithfully preserved by the city's inhabitants, as mentioned by Lucian.