Fengning Manchu Autonomous County (Chinese: 丰宁满族自治县; Manchu: ᡶᡝᠩ ᠨᡳᠩ ᠮᠠᠨᠵᡠ ᡠᡴᠰᡠᡵᠠ ᠪᡝᠶᡝ ᡰᡥᡳ ᠰᡳᠶᠠᠨ) is a Manchu autonomous county of northern Hebei province, bordering Beijing to the southwest and Inner Mongolia to the north, and lying under the administration of the prefecture-level city of Chengde.

It is the second-largest county of Hebei in terms of area, after the neighbouring Weichang Manchu and Mongol Autonomous County.

Fossils from the Jinfengopteryx, a genus of dinosaur, were discovered in Fengning Manchu Autonomous County. Other dinosaur fossils discovered in the autonomous county include one belonging to the ceratopsia suborder, and one of a stegosaurus, which both date back to approximately 130,000 million years ago. The area belonged to the wider Jehol Biota ecosystem.

Evidence suggests of human activity in the area of present-day Fengning Manchu Autonomous County dates back to approximately 30,000 to 50,000 years ago. Archaeological sites from the Hongshan culture and the Shanrong have been found in the autonomous county.

In 1735, the 13th year of the Yongzheng Emperor's, the Siqi Subprefecture (simplified Chinese: 四旗厅; traditional Chinese: 四旗廳; pinyin: Sìqí Tīng) was established in the area. In 1778, the area was reorganized as Fengning County (simplified Chinese: 丰宁县; traditional Chinese: 豐寧縣; pinyin: Fēngníng Xiàn).

In 1987, the State Council approve re-designating Fengning County as Fengning Manchu Autonomous County.

Fengning Manchu Autonomous County is bordered by Beijing to the south and Inner Mongolia to the north. The autonomous county is located at the northern edge of the Yan Mountains, and the southern edge of the Inner Mongolia Plateau [zh].

The Chao River [zh], a tributary of the Chaobai River, and the Luan River both originate within the autonomous county.