The Battle of Al-Zallaqa (479 A.H.) is one of the most important historical events in Andalusia during the Islamic middle centuries. It was the first challenge of Crescent and Cross in Andalusia between the new Islamic dynasty of Almoravid, led by Yusuf ibn Tashfin, and the Christians commanded by Alfonso VI, which determined the future of the political path of both Muslims and Christians for the next centuries. Employing a descriptive-analytical approach, this study attempts to answer two central questions: Why does the Battle of Al-Zallaqa hold particular significance among Muslim-Christian conflicts? What were its long-term consequences for Muslims in Andalusia? The findings reveal that the Battle of Al-Zallaqa was a crucial precursor to later Crusades, with the Almoravids achieving a decisive victory that reinforced religious prejudice. They also established unity in the region, putting an end to the Andalusian city-state system. Furthermore, the Almoravids’ leadership facilitated renewed ties between Andalusia and the Abbasid Caliphate, fostering broader Muslim solidarity after a prolonged period of political fragmentation. This unification delayed the Christian reconquest of Andalusia, extending Muslim rule in the region for several more centuries.