This paper aims to analyse the evolution of public debt in South Africa using new and original methods. The case of South Africa has been little studied in the literature on debt because the level of debt in this country remains reasonable. Moreover, the use of non-standard methods allows for a fine-grained analysis of the public debt time series and, consequently, to draw unprecedented conclusions. Using the Multifractal Detrended Fluctuation Analysis (MF-DFA) method borrowed from solid-state physics and medicine, we conclude that South Africa's debt has a multifractal character, which originates from the long memory effect. Thus, South Africa's public debt is unsustainable. The inefficiency of this market has been particularly exacerbated by the various shocks throughout the sample period.