The need for tolerance and peaceful coexistence in societies enriched by cultural, national, and ethnic diversity remains one of the most urgent and significant challenges facing humanity. This need is especially pronounced in an era where violence often overshadows understanding, and conflicts fueled by religious or ethnic differences continue to intensify. The increasing interconnectedness of modern societies underscores the necessity of embracing tolerance as a foundation for building harmonious and inclusive communities. This research examines Said Nursi's profound insights into the Islamic heritage of tolerance, forgiveness, and the acceptance of others, as elaborated in his masterwork, The Letters of Light/ Risale-i Nur. Nursi's vision does more than advocate for peaceful coexistence—it establishes a transformative framework for dialogue, mutual understanding, and openness to diversity. He demonstrates how societal multiplicity can evolve into harmonious unity by upholding the noble principle of tolerance, which lies at the very heart of Islamic teachings. The study also explores key concepts integral to Nursi's perspective on tolerance, such as justice, which ensures fairness and equity; mercy, as a vital ethical and spiritual value; and peaceful coexistence, as the goal of fostering unity amidst diversity. By delving into these interconnected principles, the research seeks to uncover how Said Nursi's vision can offer valuable pathways for addressing contemporary challenges in multicultural and diverse societies." Key words: Tolerance - Justice- Merci- Peace