The term Latgalians refers to the present-day inhabitants of the region of Latgale. The Latgalians are the original Latvians. They are the descendents of the ancient Latvians (then referred to as Letthi and Letthigalli in the ancient chronicles written in Latin). The chroniclers distinctly identify them as the first people to be called Latvians (Letthi). They were one of the ancient Baltic tribes who lived in the central and eastern part of present-day Latvia. Besides the Letthigalli the other tribes were the Kurs, Livs, Seli or Selonians and the Semigalians. They are of neo-European origin. The Letthigalli, who were the largest of these tribes, had a leading role, along with the the Seli, in the development of the Latvian people. Their territory extended over the area of present-day Latgale and eastern Vidzeme and included land now located in Western Russia and Belarus. Historically Latgale (Latgola, in the Latgalian language) comprises the territory of Eastern Latvia and some parts of nearby present-day Russia.

The Latgalians have a history, culture, religion and tradition that is very closely related to, yet separate from that of the Latvian inhabitants of the other regions, Kurzeme, Vidzeme and Zemgale. They speak Latgalian, a language with its own literary tradition which is distinct from Latvian. Also while much of the rest of Latvia became Lutheran as a result of the Reformation Latgale remained Catholic. The modern designation of Latgalians for the inhabitants of Latgale came into common usage in the last part of the nineteenth century.

At the start of the twentieth century Latgale comprised of the districts of Daugavpils, Rezekne and Ludza and the western parts of Drisa and Sebezha situated in the northwestern part of the old Vitebsk province (guberniya) of the Russian Empire. The number of Latgalians throughout the twentieth century has been about one-half million people.