The Bhandarkhal massacre was a political massacre that occurred in Bhandarkhal garden of Hanuman Dhoka, Kathmandu in 1806. The chief perpetrator of the massacre was then Kaji Bhimsen Thapa. Bhimsen instigated the massacre as investigation and trial upon the death of then reigning Mukhtiyar and former King Rana Bahadur Shah. It began when Tribhuvan Khawas (Pradhan), a member of Sher Bahadur's faction, was imprisoned on the re-opened charges of conspiracy with the British that led to Knox's mission and finally convicted with a death penalty on the charge of treason. After the implication, Tribhuvan decided to reveal everyone that was involved in the dialogue with the British on his house meeting on the night of 25 April 1806. The confession implicated Sher Bahadur Shah, Rana Bahadur's step-brother and he began to harass his stepbrother. Unable to bear desperation, Sher Bahadur killed Rana Bahadur and triggered the massacre which lasted for two weeks. The number of deaths occurred was ninety-three people.

Bhimsen Thapa was a Nepalese statesman who served as the Mukhtiyar and de facto ruler of Nepal from 1806 to 1837. He is widely known as the longest-serving prime minister of Nepal and was inducted into the "National heroes of Nepal" by King Mahendra Bir Bikram Shah.