Little Russia, also known as Lesser Russia, Malorussia, or Little Rus', is a geographical and historical term used to describe Ukraine.

At the beginning of the 14th century, the patriarch of Constantinople accepted the distinction between what it called the eparchies of Megalē Rosiia (lit. 'Great Rus, Great Russia') and Mikrà Rosiia (lit. 'Little Rus, Little Russia'). The jurisdiction of the latter became the metropolis of Halych in 1303. The specific meaning of the adjectives "Great" and "Little" in this context is unclear. It is possible that terms such as "Little" and "Lesser" at the time simply meant geographically smaller and/or less populous, or having fewer eparchies. Another possibility is that it denoted a relationship similar to that between a homeland and a colony (just as "Magna Graecia" denoted a Greek colony).

The name went out of use in the 15th century as distinguishing the "Great" and "Little" was no longer necessary since the Russian Orthodox Church based in Moscow was no longer tied to Kiev. However, with the rise of the Catholic Ruthenian Uniate Church in the Polish-Lithuanian Commonwealth, Orthodox prelates attempting to seek support from Moscow revived the name using the Greek-influenced spelling: Malaia Rossiia ('Little Russia'). Then, "Little Russia" developed into a political and geographical concept in Russia, referring to most of the territory of modern-day Ukraine, especially the territory of the Cossack Hetmanate. Accordingly, derivatives such as "Little Russian" (Russian: Малоросс, romanized: Maloross) were commonly applied to the people, language, and culture of the area. A large part of the region's elite population adopted a Little Russian identity that competed with the local Ukrainian identity. The territories of modern-day southern Ukraine, after being annexed by Russia in the 18th century, became known as Novorossiya ('New Russia').

After the collapse of the Russian Empire in 1917, and with the amalgamation of Ukrainian territories into one administrative unit (the Ukrainian People's Republic and then the Ukrainian Soviet Socialist Republic), the term started to recede from common use. Today, the term is anachronistic, and many Ukrainians regard its usage as offensive.

The toponym is adapted from the Greek term, which was used in medieval times by the patriarchs of Constantinople from the beginning of the 14th century. The Byzantines accepted the distinction between Μεγάλη Ῥωσσία (Megálē Rhōssía, lit. 'Great Rus', Great Russia'), meaning the northern or outer region, and Μικρὰ Ῥωσσία (Mikrà Rhōssía, lit. 'Little Rus', Little Russia'), meaning the southern or inner region. From 1448, the former became ecclesiastically independent as the Russian Orthodox Church based in Moscow declared autocephaly, and from 1458, the latter had its own metropolitans who were approved by the patriarch of Constantinople. Previously, the jurisdiction of the latter had become the metropolis of Halych in 1303. By the early 15th century, the terms disappeared and Great Russia would not re-appear in sources until during the 16th century, while Little Russia would not re-appear until the end of that century.

Initially Little or Lesser meant the nearer part, as after the division of the metropolis (ecclesiastical province) in 1305, a new southwestern metropolis in the Kingdom of Galicia–Volhynia consisted of only 6 of the 19 former eparchies. It later lost its ecclesiastical associations and became a geographical name only. Zygmunt Gloger, in his Geography of Historic Lands of Old Poland (Polish: Geografia historyczna ziem dawnej Polski), describes an alternative view of the term Little in relation to Little Russia, where he compares it to the similar term Little Poland.

In Russian, the notion of Rossiia, which was used as the common designation for the multinational Russian Empire and for the modern Russian state, is closely related to the older terms Rus and russkii. Rossiia is distinguished from the ethnonym russkii, as Rossiia refers to a supranational identity, among them ethnic Russians. During the imperial era, Rossiia referred to a multinational state, while the ethnic term russkii officially included all East Slavs, namely the Great Russians, Little Russians and White Russians. In this sense, the Ukrainians, who were known as Little Russians, were part of an all-Russian identity. The rise of modern Russian nationalism created the concept of an ethnic Russian nation with the political concept of the Russian Empire, which was aimed at a new project of an ethnically homogeneous nation-state.

The term was used by Patriarch Callistus I of Constantinople in 1361, when he created two metropolitan sees: Megalē Rosiia (lit. 'Great Rus, Great Russia') and Mikrà Rosiia (lit. 'Little Rus, Little Russia'). The former referred to the province of Moscow and Vladimir, while the latter referred to the province of Halych and Kiev. King Casimir III of Poland was called "the king of Lechia and Little Rus". Yuri II Boleslav used the term in a 1335 letter to Dietrich von Altenburg, the Grand Master of the Teutonic Knights, where he styled himself as dux totius Rusiæ Minoris. According to Mykhaylo Hrushevsky, the term was associated with the Kingdom of Galicia–Volhynia, and after its downfall, the name ceased to be used.