ABSTRACT Introduction: The HIV care cascade examines the attrition of people living with HIV from diagnosis, to the use of antiretroviral therapy (ART) and suppression of viral replication. UNAIDS defined the "90-90-90" targets to be reached by the end of 2020: 90% of people living with HIV (PLWH) are aware of their status, 90% of those diagnosed initiate ART and 90% of those on ART achieve an undetectable viral load. We reviewed the literature from sub-Saharan Africa to assess definitions used for the steps in the HIV care cascade. Methods: We searched PubMed, Embase and CINAHL for articles published from January 2004 up to December 2020. Longitudinal and cross-sectional studies were included if they reported on at least one step of the UNAIDS 90-90-90 cascade or at least two steps of a detailed 7-step cascade. A step was clearly defined if authors reported definitions for numerator and denominator, including the description of the eligible population, and methods of assessment or measurement. The review protocol was registered in Prospero. Results: Overall, 3,364 articles were screened for eligibility; 82 studies met the inclusion criteria. Nineteen countries were represented; most studies were from Southern (38 studies, 34 from South Africa) and East Africa (29 studies). Fifty-eight studies (71.6%) were longitudinal, with a median follow-up of three years. The medium number of steps covered by each study out of 7 steps was 3 (interquartile range [IQR] 2-4) and the median year of publication 2015 (IQR 2013-2019). The number of different definitions for the numerators ranged from four definitions (for step "diagnosed and aware of HIV status") to 21 (step "viral suppression"). The number of different definitions for the denominators ranged from two definitions (step "People living with HIV") to 21 (step "viral suppression"). Only twelve studies assessed all three of the 90-90-90 steps. Conclusions: The various definitions used for numerators and denominators across different studies mean that the proportions of patients retained at each step of the HIV care cascade cannot easily be compared between studies, countries and time periods, nor meta-analyzed. There is a need for standardization of methods and definitions. PROSPERO Number: CRD42017055863