Kasi (Pushto; Pashto: کاسي) is a Pashtun tribe from the Sarbani tribal confederacy, primarily found in Quetta, Pakistan and Nangarhar, Afghanistan.as well as in Iran, Palestine, Iraq.
Kasi is a tribe of Pashtuns which is primarily concentrated in and around Quetta city. It is also spelled as Kansi. They belong to the Saraban division of Pashtuns. It is numerically a very small tribe, they only numbered 1064 souls in 1901 AD ("Quetta-Pishin Gazetteer, 1901, p-73).
The Kasi tribe is divided into eight sections, namely, khawajzai, Achozai, Gadazai,Ahmad Khanzai, Akazai, Badazai, Mirzai, Shinwari, and Spingull.
According to Ain-i-Akbari of Abu Fazal (written around 1590 AD), Shal & Mastung was dependency of Kandahar in later half of sixteenth century. Shal had mud fort at that time and its lands were assessed at four and half tumans in money, 940 sheep and 780 kharwars in grain. The Kasi Afghans and Baluchs of Shal- Mastung had to furnish 1,000 horse and 1,000 foot.
In the reign of Shahjahan (1628–1655) Rajo and Zangi, Rind chiefs raided Shal by way of the Bolan. They were defeated by the Kasis after a severe engagement about three miles south of Quetta. Since then the small stream of Zangi Lora was given its name, as the action took place at its source when Zangi, the Rind chief, was killed.
The leading families of Kasis are known as Arbabs. In 18th century Ahmad Shah Abdali conferred the office of Arbab upon Muhammad Thalib Kasi. Mir Mahabat Khan (ruler of Kalat) killed him when he was at village Katir. The Kasi Arbab was engaged in collecting the revenue at the time and was quite unprepared for the attack. News of the occurrence immediately was despatched to Kandahar, and Ahmed Shah Durrani summoned Mahabat Khan to Kandahar to explain how he came to slay the Shah's representative in Shal. [<ref>https://pashtunhistory.com/kasi-tribe/</ref>]