The 6.5×50 Arisaka, or more correctly, 6.5x50mmSR Arisaka is a semi-rimmed rifle cartridge with a 6.5 mm diameter bullet. It was the standard Japanese military cartridge from 1897 until the late 1930s for service rifles and machine guns when it was gradually replaced by the 7.7×58mm Arisaka.
The 6.5x50mmSR was first introduced as the Type 30 cartridge with a round-nosed bullet by the Imperial Japanese Army in 1897 for the newly adopted Type 30 Arisaka infantry rifle and carbine. The new rifle and cartridge replaced the 8×52mm Murata round used in the Type 22 Murata rifle. In 1902, the Imperial Japanese Navy also adopted the 6.5x50mmSR for their Type 35 rifles. In 1907, a spitzer round was adopted as the Type 38 cartridge for all subsequent Japanese service small arms in 6.5mm caliber.