Abstrak: Persoalan tentang fajar merupakan pembahasan klasik yang penting dalam penentuan waktu ibadah, khususnya salat subuh dan puasa. Artikel ini mengkaji koherensi antara dalil naqli (al-Qur'an dan hadis), pendapat imam mazhab, dan temuan astronomi modern dalam memaknai fajar. Melalui kajian tekstual dan observasi ilmiah, ditemukan bahwa fajar shadiq ditandai dengan cahaya putih horizontal di ufuk timur, sedangkan fajar kadzib adalah cahaya vertikal yang menjulang ke langit. Imam empat mazhab sepakat terhadap karakteristik dasar fajar shadiq, meskipun variasi kecil terkait warna dan sifat cahaya tetap ada. Sementara itu, astronomi modern menunjukkan bahwa fajar kadzib tidak selalu disusul oleh kegelapan, berbeda dari deskripsi klasik. Perbedaan ini kemungkinan dipengaruhi oleh faktor geografis dan kondisi atmosfer. Analisis ini menunjukkan bahwa meskipun terdapat variasi pemaknaan, ketiga pendekatan tersebut sepakat bahwa fajar shadiq menjadi penanda sahnya pelaksanaan salat subuh. Penelitian ini menegaskan pentingnya integrasi antara sumber syar'i, pendapat ulama, dan observasi astronomis dalam memahami fenomena fajar secara lebih akurat dan kontekstual.Kata kunci: Fajar, dalil naqli, imam mazhab, astronomi, waktu salat subuh Abstract: The issue of dawn is an important classic discussion in determining the time of worship, especially dawn prayers and fasting. This article examines the coherence between the postulates of naqli (the Qur'an and hadith), the opinions of madhhab imams, and the findings of modern astronomy in interpreting dawn. Through textual studies and scientific observations, it was found that the dawn of shadiq is characterized by a horizontal white light on the eastern horizon. In contrast, the dawn of kadzib is a vertical light that rises into the sky. The imams of the four schools agree on the basic characteristics of dawn shadiq, although minor variations regarding the color and nature of light remain. Meanwhile, modern astronomy shows that the dawn of kadzib is not always followed by darkness, different from the classical description. Geographical factors and atmospheric conditions likely influence this difference. This analysis shows that although there are variations in meaning, the three approaches agree that the dawn of shadiq is a marker of the validity of the implementation of the dawn prayer. This research emphasizes the importance of integration between shari'i sources, scholars' opinions, and astronomical observations in understanding the dawn phenomenon more accurately and contextually.Keywords: Fajar, postulation of naqli, imam madhhab, astronomy, time of dawn prayer