Although sub-Saharan African countries comprise a large amount of low-grade phosphate rock (PR), they do not consume this because of the high cost of P fertilizer processing. For less expensive P fertilizers, a suitable processing method must be selected for each low-grade PR. As phosphate solubility and suitable processing differ by PR, ten low-grade African PRs were collected from different countries and analyzed. Their phosphate solubilities correlated with their chemical and mineralogical compositions. Based on mineral composition-related results supported by TG-DTA and XRD analyses, we broadly classified the ten low-grade African PRs into five groups. These low-grade PRs consisted mainly of hydroxyapatite and were suitable for direct application to agricultural land as powdered PR. Low-grade PRs with low Fe and Al contents are suitable for partial acidulation and may be effective, whereas low-grade PRs with high Fe, Al, and heavy metal contents are suitable for high-temperature treatment. Regardless of the difference in origin, the phosphate solubility of low-grade African PRs is indicated by 2% citric acid solubility, assuming a dependence on the crystallite sizes of francolite and fluorapatite.