Hoboksar Mongol Autonomous County (Chinese: 和布克赛尔蒙古自治县; pinyin: Hébùkèsài'ěr Měnggǔ Zìzhìxiàn), sometimes referred to by the historic name Hefeng County (和丰县; Héfēng Xiàn), is an autonomous county for Mongols in the middle-north of Xinjiang Uyghur Autonomous Region, Western China. It is under the administration of Tacheng Prefecture. The county has an area of 28,784 km² (11,114 sq mi) with a population of 62,100 (as of 2010 Census). It has eight towns and townships and seven farms; Hoboksar Town is the county seat.

The name Hoboksar (Ховогсайр) is a portmanteau of "Hobok" (ховог) and "Sar" (сайр) from the Mongolian language. Hobok refers to the Hobok River and means "sika deer"; the river was named after its river basin within huge amount of sika deer in the past. Sar refers to the Salair Mountains and literally means "horseback"; the mountain was named after its shape, which resembles a horseback.

At the latest starting from the Qin dynasty, the Saka people appeared in the place of present Hoboksar area. This was followed by the Usans and Xiongnu people.

The place was part of Usan State in the Western Han period. It was merged to the Rear Jushi Kingdom (車師後國) in the Eastern Han and Three Kingdoms periods. It was part of Xianbei during the Jin period, part of Rouran Khaganate, followed by the First Turkic Khaganate, Western Turkic Khaganate in the period of Northern and Southern dynasties. It was under the administration of Kunling Protectorate (崑陵都護府) of the Tang dynasty in 657, ruled by Karluks in 789, Uyghur Khaganate in 808, Kyrgyz Khaganate in 840 and Qara Khitai in 1127, it was merged to the Yuan dynasty in 1218, became the dominion of Ögedei Khan in 1225, then after that, the territory of Beshbalik Province (Beiting) and Almaliq Province in 1280, it was merged to Chagatai Khanate during 1324 – 1328.

It was part of Eastern Chagatai Khanate (Beshbalik Khaganate) in 1370, the herd land of the Oirats tribe in the 5th century. After Batur's succession to Khong Tayiji in 1636, he quickly unified the Oirats tribes in the North Xinjiang, with Hoboksar as the base camp. Batur built a castle five kilometers away southeast of the present county seat of Hoboksar Town between 1639 – 1643.

The place of Hoboksar was under jurisdiction of Tarbaghatay Ministerial Attache (塔爾巴哈臺參贊大臣, under leadship of the General of Ili; "Tarbaghatay", the present Tacheng Prefecture) in 1758. The Torghut Tribe back far away from the south side of Russian Volga River, immigrated to Hoboksar in 1771.

Hoxtolgay Xianzuo (和什托洛蓋縣佐, similar to a division under vice county magistrate; in the present Hoxtolgay Town) under jurisdiction of Shawan County, was formed in 1915 and it was transferred to Tacheng Circuit (塔城道) in 1916. Hoxtolgay Xianzuo was changed to Hoxtolgay Division (和什托洛蓋設治局) and the Hefeng Division (和豐設治局) was formed in 1941. Hefeng County (和豐縣) was organized in 1944 and its county seat is in the present Hoboksar Town. Hefeng County was renamed to Hoboksar Mongol Autonomous County on September 10, 1954.

Hoboksar County is located south of the Tarbagatai-Saur mountain range and its northern part, where most of the county's population lives, receives some water from streams (such as the Baiyang River) flowing from the snow-capped mountains. The southeastern part of the county is in Gurbantünggüt Desert.