Abstract: The Dynamics of Sunnah Authority as a Source of Islamic Law. The development of Islamic law to respond to social changes had caused the authority of the Sunnah experience a dynamic evolution. At first, the sole autoritative Sunnah, as the source of law, was the Sunnah of the Prophet. In the era of companions, however, the Sunnah also included behavior and decisions made by the prophet’s companions. In the era of post-Companions, the religious opinions made by judges or the rulings were also considered as Sunnah as they were also based on the Sunnah of the Prophet. Thus, a variety of the Sunnah emerged at the same time in several regions. Facing with this phenomenon, a number of muslim scholars such as: al-Syâfi’i, al-Qarâfi, Yûsuf al-Qaradhâwi, evaluate the authority of the Sunnah and distinguish them to be the one which is still authoritative to be carried out (ma’mûl bih) and the other one which no longer can be carried out (ghair ma’mûl bih). Abstrak: Dinamika Otoritas Sunnah Nabi Sebagai Sumber Hukum Islam. Perkembangan hukum Islam dalam merespon berbagai perubahan sosial menyebabkan otoritas Sunnah Nabi mengalami evolusi yang dinamis. Pada awalnya, Sunnah yang otoritatif sebagai sumber hukum hanyalah Sunnah Nabi. Pada era sahabat, Sunnah juga mencakup perilaku dan putusan-putusan sahabat. Pada era Pasca Sahabat, fatwa ulama atau putusan hakim pengadilan juga diangap sebagai Sunnah karena diyakini masih tetap bersumber dari Sunnah Nabi. Oleh karena itu muncul berbagai sunnah-sunnah lokal yang berbeda. Menghadapi fenomena ini, sejumlah ulama’/intelektual Muslim seperti: al-Syâfi’i, al-Qarâfi, Yûsuf al-Qaradhâwi, memberikan pendapat tentang otoritas Sunnah dan membedakan mana Sunnah yang masih ma’mûl bih atau otoritatif untuk diamalkan dan ada yang sudah ghair ma’mûl bih atau tidak dapat diamalkan lagi.