Al-Qadir Billah was the fourth caliph of the Fatimid Caliphate, ruling from 991 to 1036 CE. He is known for his efforts to consolidate power and promote the Ismaili branch of Islam. His reign was marked by significant cultural and architectural developments, including the construction of mosques and public works. During his rule, Al-Qadir Billah faced various challenges, including internal dissent and external threats. He worked to strengthen the caliphate's military and administrative structures, ensuring its stability. His leadership contributed to the Fatimid dynasty's influence in North Africa and the Mediterranean region.