Jochi (Mongolian: ᠵᠦᠴᠢ; c. 1182 – c. 1225), also spelled Jüchi, was a prince of the early Mongol Empire. His life was marked by controversy over the circumstances of his birth and culminated in his estrangement from his family. He was nevertheless a prominent military commander and the progenitor of the family who ruled over the khanate of the Golden Horde.

Jochi was the son of Börte, the first wife of the Mongol leader Temüjin, now Genghis Khan. For many months before Jochi's birth, Börte had been a captive of the Merkit tribe, one of whom forcibly married and raped her. Although there was thus considerable doubt over Jochi's parentage, Temüjin considered him his son and treated him accordingly. Many Mongols, most prominently Börte's next son Chagatai, disagreed; these tensions eventually led to both Chagatai and Jochi being excluded from the line of succession to the Mongol throne.

After Temüjin founded the Mongol Empire in 1206 and took the name Genghis Khan, he entrusted Jochi with nine thousand warriors and a large territory in the west of the Mongol heartland; Jochi commanded and participated in numerous campaigns to secure and extend Mongol power in the region. He was also a prominent commander during the invasion of the Khwarazmian Empire (1219–1221), during which he subdued cities and tribes to the north. During the 1221 Siege of Gurganj, tensions arose between him, his brothers, and Genghis, which never healed. Jochi was still estranged from his family when he died of ill health c. 1225. His son Batu was appointed to rule his territories in his stead.

Jochi's mother, Börte, was born into the Onggirat tribe, who lived along the Greater Khingan mountain range south of the Ergüne river, in modern-day Inner Mongolia. At the age of ten, she was betrothed to a Mongol boy named Temüjin, son of the Mongol chieftain Yesugei. Seven years later (c. 1178), after he had survived a violent adolescence, they married. They had their first child, a daughter named Qojin, in 1179 or 1180. By forming alliances with notable steppe leaders, such as his friend Jamukha and his father's former ally Toghrul, and with the help of his charisma, Temüjin began to attract followers and gain power. Word of his rise spread and soon drew the attention of the Merkit tribe to the northwest, from whom Yesugei had abducted Temüjin's mother Hö'elün, sparking a blood feud; they resolved to take revenge on Yesugei's heir.

Because of their consequences, the subsequent events were considered controversial: most contemporary authors omitted any mention of the events, while the two that did include them (the Secret History of the Mongols, a mid-13th-century epic poem, and the 14th-century Persian historian Rashid al-Din's Jami al-tawarikh) are contradictory. The following narrative, containing elements from both, is considered most plausible. In 1180 or 1181, a large force of Merkits raided Temüjin's camp; while most of his family managed to escape, Börte was captured. She was forcibly married to Chilger-Bökö, the younger brother of Hö'elün's original husband. Meanwhile, Temüjin had convinced his allies to assemble substantial forces to help him rescue Börte. Under Jamukha's command, the combined army campaigned against the Merkits and defeated them, recovering Börte and taking large amounts of plunder.

Börte was heavily pregnant and c. 1182 gave birth to Jochi in Jamukha's camp. As Chilger-Bökö had undoubtedly raped her, and as she had been among the Merkits for nearly nine months, Jochi's paternity was uncertain; this was reflected in his name, meaning "guest" in Mongolian. While Temüjin always regarded Jochi as his son by blood and treated him accordingly, many Mongols, such as his younger brother Chagatai, viewed him as a bastard sired by Chilger-Bökö.

Jochi does not reappear in historical sources until 1203. By this time, he was old enough for marriage. Temüjin intended to betroth him to a daughter of his ally Toghrul, but because of Jochi's uncertain birth and Temüjin's comparatively low status, this proposal was taken as insulting by Toghrul's people and eventually led to war between the two leaders. After Toghrul's defeat in 1204, Jochi was given one of his nieces, Begtütmish, as a wife. He also married other women: Börte's niece Öki; her relative Sorghan; and several less powerful women, namely Qutlugh Khatun, Sultan Khatun, Nubqus, Shīr, Qarajin, and Kul. In addition, Jochi took concubines. It is unknown who Jochi's senior wife was, but it was likely either Öki or Sorghan.

Jochi's most important sons were Orda Khan and Batu Khan; they were the children of Sorghan and Öki respectively. Neither these women nor Begtütmish was the mother of Jochi's other notable son, Berke. The names of eleven other sons are known, but none had significant careers, reflecting the junior status of their mothers. Descendants of younger sons nevertheless used their Jochid lineage to legitimise their right to rule: these included Khiḍr Khan of Shiban's line, and Tokhtamysh who descended from Jochi's youngest son Tuqa-Timur.