In this study, our objective was to analyze the chemical composition of aqueous extracts from the aerial parts of four plants: Mentha spicata L., Mentha piperita L., Mentha pulegium L., and Ocimum basilicum L., and to evaluate their antifungal activity against certain phytopathogenic fungi, specifically Alternaria alternata, Wickerhamomyces anomalus, Fusarium proliferatum, and Rhizoctonia solani, which were isolated from post-harvest potato tubers from the El Oued region (northern Sahara, eastern Algeria). Maceration with agitation for 24 hours was employed to obtain the aqueous extracts. The results revealed that the yield varied between 0.13% and 0.27%. Phytochemical tests conducted on the aqueous extracts highlighted the presence of various chemical compounds such as tannins, flavonoids, saponins, and alkaloids. The content of total phenolics of different plants extracts was in the range of 3.277 - 11.124 mg. while the content of total flavonoids of the different plants extracts was in the range of 0.896 - 2.312 mg. HPLC analysis revealed that the aqueous extract of M. piperita is composed of acetylsalicylic acid, chlorogenic acid, and p-coumaric acid, whereas M. pulegium is characterized by the presence of acetylsalicylic acid, caffeine, and pyrogallol. O. basilicum contains gallic acid. The aqueous extracts were tested for their antifungal activity using the direct contact method against the mycelial growth of the tested strains. The results revealed a strong antifungal potential against these strains. At concentrations of 1.5%, 2%, 3.5%, and 4%, the aqueous extract of Mentha spicata exhibited a 100% antifungal effect on all four fungi. Regarding Mentha piperita, the aqueous extract at 1% caused total inhibition (100%) of Alternaria alternata and Wickerhamomyces anomalus, and at 4% for Fusarium proliferatum and Rhizoctonia solani. We observed a fungicidal inhibitory effect (100%) at 1.5% for Alternaria alternata and Wickerhamomyces anomalus, and at 3.5% for Fusarium proliferatum and Rhizoctonia solani with the aqueous extract of Mentha pulegium. The aqueous extract of Ocimum basilicum resulted in total inhibition (100%) at concentrations of 2%, 2.5%, 5.5%, and 7.5% for Wickerhamomyces anomalus, Alternaria alternata, Fusarium proliferatum, and Rhizoctonia solani respectively. The results obtained pave the way for the exploitation of the aerial parts of the investigated plants as an alternative to synthetic chemical fungicides.