French mathematician who, at age 15, solved a difficult problem about cycloids posed by Pascal. He published the first book ever on differential calculus, L'Analyse des Infiniment Petits pour l'Intelligence des Lignes Courbes (1696). In this book, l'Hospital included l'Hospital's rule. l'Hospital's name is commonly seen spelled both "l'Hospital" and "l'Hôpital" (e.g., Maurer 1981, p. 426), the two being equivalent in French spelling.

Additional biographies: MacTutor (St. Andrews), Dublin Trinity College