This paper provides a comparative and diachronic account of reflexive morphology in the Kikongo language cluster, a genealogically closely related group of 40+ West Coastal Bantu languages. This study is based on data from 34 grammatical descriptions from 1659 to 2017 and fieldwork data collected in 2012 and 2015. Previous studies have shown that Kikongo languages, despite being closely related to each other, demonstrate extensive phonological and morphological variation. This is also the case for reflexive morphology. First, six different reflexive prefixes are attested in the database. These are, in alphabetical order, di- (with cognate li-), ké-, ki-, ku-, lu- and a vocalic morpheme variably written as i-, ii- or yi-. Second, while most Kikongo languages have one reflexive prefix, some descriptions report the use of two or more different prefix forms in a single language. Languages with multiple reflexive prefixes fall into two groups: one group has different prefixes in free alternation, while the overall verbal construction is claimed to determine which prefix is used in the other group. Following an overview of the formal variation, I discuss the possible origins of the various reflexive prefixes. One hypothesis assumes that the vocalic prefix is inherited from Proto-Kikongo, the most recent common ancestor of the Kikongo languages. A second hypothesis relates the origin of some reflexive prefixes to object indexes of various noun classes, in particular, noun classes 5, 7 and 11. A third hypothesis suggests that in some Kikongo languages, the vocalic reflexive prefix became fused with other pre-stem verbal morphology and developed into ku- and ki-. A fourth hypothesis proposes the development of the reflexive prefix ké- from an auxiliary. These four hypotheses are not mutually exclusive, and I discuss how multiple diachronic scenarios are necessary to account for the full range of variation of reflexive morphology in the Kikongo language cluster. It is proposed that the distribution of di-/li- and ki- is contact-induced through borrowing, both between different Kikongo languages and between Kikongo and non-Kikongo languages. I tentatively reconstruct the vocalic reflexive prefix *i- to Proto-Kikongo.