A 21-year-old man developed an infectious keratitis after swimming in Spain whilst wearing contact lenses. Mycelial growth from a corneal sample suggested keratomycosis but a drastic worsening of the patient's condition was observed on antifungal drugs. At day 38, the Pan-fungal PCR identified P. insidiosum, which is an aquatic organism belonging to the oomycete family. Based on recent literature, our patient was promptly prescribed systemic and local antibiotic regimen and cure was ultimately achieved. In order to facilitate P. insidiosum identification in future cases, we have generated the first MALDI-TOF MS reference spectrum for Pythium insidiosum. This MALDI-TOF-MS reference spectrum is planned to be deposited on an open-access-platform and should allow immediate identification of the pathogen. Finally, this case report also demonstrates that P. insidiosum is emerging outside tropical and subtropical areas. Clinicians and microbiologists should have better knowledge to accurately manage and diagnose this sight-threatening infection.