Mù Cang Chải is a rural district of Yên Bái province, in the Northwest region of Vietnam. As of 2019, the district had a population of 63,961, …Mù Cang Chải is a rural district of Yên Bái province, in the Northwest region of Vietnam. As of 2019, the district had a population of 63,961, covering an area of 1199 km². The district capital lies at Mù Cang Chải.