Kailu County (Mongolian: ᠺᠠᠶᠢᠯᠦ ᠰᠢᠶᠠᠨ; Chinese: 开鲁县) is a county in the east of Inner Mongolia, China.

It is under the administration of Tongliao City, 76 kilometres (47 mi) to the east, and China National Highway 303 passes through it.

As the traditional seat of Ar Khorchin, East Jaruud and West Jaruud, the 3 areas are abbreviated in Chinese as the 3 R's since each contains the word R transcribed as "LU" in Chinese.

Others: Kailu County features a cold semi-arid climate (Köppen BSk), marked by long, very cold and dry winters, hot, somewhat humid summers, and strong winds, especially in spring.

The annual precipitation is 327.4 millimetres (12.9 in), with nearly half of it falling in July and August alone.