The delayed diversification of early animals until the middle Ediacaran Period, despite their likely origin in the Cryogenian Period or earlier, has been attributed to low levels of dissolved O₂ in global seawater. To provide more robust constraints on the extent of global-ocean oxygenation during the mid-Cryogenian Period, we analyzed paired U (δ²³⁸U) and Mo (δ⁹⁸Mo) isotope compositions of organic-rich shale in the basal Datangpo Formation from two separate drillcores in South China. This unit yielded an average δ²³⁸U of −0.39 ± 0.23‰ (2SD; relative to standard CRM145), which is significantly lower than the average δ²³⁸U (+0.02 ± 0.12‰) of euxinic sediments of the modern restricted Black Sea and well below a modeled δ²³⁸U of +0.2‰ for modern unrestricted euxinic facies (e.g., Saanich Inlet). The U/Al ratios of our samples indicate that ~ 40% of U was derived from detrital materials (δ²³⁸U_detrital = ~−0.3‰), suggesting that the δ²³⁸U of authigenic U is even lower than the measured bulk-sample values. Taking into consideration the 0.4–0.8‰ enrichment of ²³⁸U in euxinic sediments relative to seawater, the δ²³⁸U values of the Datangpo shales correspond to contemporaneous seawater δ²³⁸U of −1.20‰ to −0.73‰. Owing to mass balance considerations, these low seawater δ²³⁸U values are indicative of widespread development of anoxia in the Cryogenian interglacial ocean (~658–654 Ma). These shales yield mostly low δ⁹⁸Mo values (+0.56 ± 0.46‰), although the youngest samples have values as high as +1.21 ± 0.23‰ (relative to NIST SRM 3134 = +0.25‰), all of which are significantly lower than modern seawater δ⁹⁸Mo (+2.34 ± 0.10‰). The Datangpo shales either directly record the global seawater δ⁹⁸Mo signature or provide a minimum estimate thereof (in the event of local influences). The consistently low δ⁹⁸Mo values of the Datangpo shales thus confirm widespread anoxia in the Cryogenian interglacial ocean. These findings based on paired δ²³⁸U-δ⁹⁸Mo analyses thus provide key information regarding global-ocean redox conditions during the interval immediately preceding the rise of macroscopic and morphologically complex animals