Objectives We examined the association between incorrect knowledge of ovulation and unintentional pregnancy and child among young women in sub-Saharan Africa countries. Methods Using Pearson's Chi-square, t test, multiple logistic regression, and likelihood ratio test, we analyzed Demographic and Health Survey data (2008-2017) of 169,939 young women (15-24 year). Results The range of prevalence of incorrect knowledge of ovulation was 51% in Comoros and 89.6% in Sao Tome and Principe, while unintentional pregnancy ranged between 9.4% in the Republic of Benin and 59.6% in Namibia. The multivariate result indicates a strong association between incorrect knowledge of ovulation and unintentional pregnancy (OR = 1.17; p \ 0.05) and unintentional child (OR = 1.15; p \ 0.05). Conclusions Adolescent women (15-19) generally have poor knowledge of ovulation and are more likely to report an unintentional pregnancy/child than women between ages 20-24. To reduce the burden of unintentional child/pregnancy in Africa, fertility knowledge should not only be improved on but must consider the sociocultural context of women in different countries that might affect the adoption of such intervention programs. Pragmatic efforts, such as building community support for young women to discuss and share their experiences with professionals and educate them on fertility and sexuality, are essential. Keywords Adolescence Á Reproductive health Á Knowledge of ovulation Á Fertility awareness Á Contraception Á Unintentional pregnancy Á Medical geography Á Africa This article is part of the special issue ''Sexual and reproductive health of young people-Focus Africa''. The Rudolf Geigy Foundation (Basel, Switzerland) funded the open access publication of this article.