军市一(β CMa / 大犬座β)是大犬座的一颗恒星，其俗名为Murzim，Mirza，Al-Murzim或Mirzam。

其俗名来源于阿拉伯语مرزم，意为“报信者”，这可能是因为其每晚在天狼星之前升起。军市一是一颗变星等的蓝白巨星，其星等以6小时的周期在1.95~2.00之间变化。它是一颗仙王座β变星。军市一处于氢聚变燃烧的晚期，之后将会耗尽其氢并开始氦聚变。

军市一位于本地泡的远端。

Beta Canis Majoris (β CMa, β Canis Majoris) is a star in the southern constellation of Canis Major, the 'greater dog', and is located at a distance of about 500 light-years (150 parsecs) from the Earth. In the modern constellation it lies at the position of the dog's head. It has the traditional name Murzim, Al-Murzim or Mirzam, which is derived from the Arabic (مرزم) for 'The Herald', and probably refers to its position, heralding Sirius in the night sky (i.e., rising before it).