Usool Shaashi is a foundational text on the principles of Islamic jurisprudence (usool al-fiqh) authored by the renowned scholar Shaykh Muhammad al-Shashi. This concise and classical work systematically presents the key rules and methodologies used to derive legal rulings from the Quran, Sunnah, consensus, and reasoning. Widely studied in traditional Islamic seminaries, it serves as an essential resource for students beginning their journey into the science of fiqh, providing clear explanations of complex concepts in a structured format.