The mai (sometimes equated to king or emperor) was the monarch of the Kanem–Bornu Empire from the foundation of the empire in the 8th century to the abolition of the office in the mid-19th century. From the conversion to Islam in the 11th century and onwards, the mai sometimes adopted additional titles, such as emir, sultan, or caliph. The last mai, Ali V Minargema, was killed in 1846, whereafter the empire was ruled by the shehus.

Records of the mais generally distinguish between an earlier Duguwa dynasty (8th–11th century) and a later Sayfawa dynasty (11th–19th century) but it is unclear whether this distinction is rooted in an actual change in royal lineage or the result of some other factor. The line of rulers is reconstructed by scholars through orally recited sources such as the girgam (the empire's royal chronicle), surviving literary sources, and contemporary sources from other parts of the Islamic world.

In the Kanem–Bornu Empire, keeping records of the royal lineage was the task of specialists, usually part of the royal court and in service of the mai. Records were passed down both through documents, written in Arabic by court scribes, and in the form of oral history. The history of the mais was referred to as the diwan in its written form and as the girgam in its orally recited form. Girgam is also commonly used as a name for both versions. Another type of important source document are mahrams, grants given by mais to their officials and subjects.

The empire was a literate society by the 12th century at the latest but surviving native literary sources are very limited in number and no known intact documents predate the 16th century. Now lost early documents include a 1392 letter from the mai of Bornu to sultan Barquq of Egypt recorded in Arab sources and a 16th-century narrative history of the reign of mai Idris III Katagarmabe by the Kanuri author Masfarma Omar ben Othman. A surviving document from the 16th century is the works of Ibn Furtu, the Grand Imam of Bornu, which detail the reign of mai Idris IV Alooma and some earlier imperial history. Limited information on Kanem–Bornu history can also be derived from contemporary Arab and North African historians, such as Ibn Sa'id al-Maghribi (1282), Ibn Battuta (1353), Ibn Khaldun (1385), al-Maqrizi (1400), and Leo Africanus (1528).

The earliest European scholar to produce a list of Kanem–Bornu rulers was the German explorer Heinrich Barth, who visited Bornu in the early 1850s. Barth's main source was a diwan which chronicled the entire history of the empire. According to Barth this was an abridged document, though he was unable to find the original larger work. Barth compared his diwan with two additional shorter diwans, as well as other works, most notably those of Ibn Furtu and al-Maqrizi, and found a "striking correspondence" and only "slight discrepancies". Barth was especially surprised by the correspondences with a list of mais in al-Maqrizi's work, which must have been based on material obtained much earlier, possibly from pilgrims or merchants that passed through Egypt.

Scholars after Barth are only partially independent from each other. The next European explorer to compose a list of rulers of Kanem–Bornu was the German explorer Gustav Nachtigal, who visited Bornu in the 1870s. Nachtigal was on the orders of the then-incumbent ruling shehu Umar Kura provided with historical documents by the courtier Ahmed ibn Brahim, and worked out his own list of mais using this material. In the early 20th century, Moïse Landeroin [fr] accompanied the 1906–1907 expedition of Jean Tilho [fr] to the Chad Basin and collected a large amount of material, including a document that gave a complete timeline of mais and significant world events. From 1904 to 1930, the British colonial administrator Richmond Palmer collected oral traditions and historical documents in northern Nigeria, which were largely published in the volumes Sudanese Memoirs (1928) and Bornu, Sahara and Sudan (1936). Palmer made use of the same source material as Barth and combined it with other sources to produce what he referred to as a "more complete" version. Palmer believed that Nachtigal's list was "very corrupt" and that Landeroin's was "suspect", having used material from secondary 19th-century sources. Palmer's work has since its publication had a strong influence on oral histories in Bornu itself, which can thus no longer be considered independent from European reconstructions.

In the 1930s and 1940s, the French historian Yves Urvoy attempted to synthesize the different sources to produce a list of mais, using Arabic sources, the work of Ibn Furtu, girgams and mahrams published by Palmer, and the lists of Barth, Nachtigal, and Landeroin. Urvoy believed that Barth's version was more reliable than those of Nachtigal and Landeroin, partly due to more alterations between lineages in the line of succession. Urvoy faced the most difficulty in reconstructing the royal line between the middle of the 13th and early 16th century, where the sources disagree the most. Similar efforts to examine and synthesize the source material to produce a list of mais as reliable as possible has since been conducted by Ronald Cohen (1966), Dierk Lange (1977), and Augustin Holl (2000).

Since girgams give only regnal years, not absolute dates, estimated dates for the reigns of the mais are derived from counting back from the known death dates of the late rulers and comparing with mais mentioned in contemporary Arab documents. Differences between modern transcriptions and translations of girgams may derive from scribal errors, faulty memories during oral recital, and faulty translations by Arab and European scholars. Many of the Kanuri names in the girgams are attributes, such as Selema ("black") and Dunama ("strong"), and may at least in some cases reflect later nicknames and not the contemporary names for rulers.