The organising institution of modern Libyan religious history is a Sufi order that became a state. The Sanusiyya was founded in the 1830s by Muhammad ibn Ali al Sanusi, and it did something unusual for a tariqa: it built a network of zawaya, lodges combining a mosque, a school, a hostel and a farm, sited on the caravan routes of the Saharan interior, and used them to mediate between tribes, teach, arbitrate disputes and trade. The order effectively administered a large part of the interior where no government reached.
That network became the framework of resistance to the Italian occupation from 1911, led in Cyrenaica by Omar al Mukhtar, a Sanusi teacher, who fought for two decades and was hanged in 1931. When Libya became independent in 1951 the head of the order became King Idris I, and the country was governed by a Sufi dynasty until 1969.
Muammar Gaddafi then curtailed the order, confiscated its endowments and closed its institutions, and advanced a religious position of his own. He rejected much of the hadith corpus in favour of the Quran alone as a legal source, an unusual stance for a head of state, and reset the calendar to date from the Prophet's death rather than from the hijra, which put Libya on a different year from the rest of the Muslim world.
The population is almost entirely Sunni and Maliki. There is a small Ibadi Berber minority in the Nafusa mountains and at Zuwara, sharing that tradition with the Algerian Mzab and with Oman, and a Jewish community, once substantial in Tripoli, that has gone entirely.